Peak district - how much forktravel for a hardtail?

I'm wanting to get back to the trails again after a prolonged period away (about 20 years!) When last I was out, I was riding a heavy 21 gear steel rigid peugeot. I had an opportunity to try a fairly stock 2012 Cube Ltd Race a while ago, the weight difference to what I used to ride was amazing, it felt exceptionally light and nimble and I think it's this what has given me that niggly bug that says I need to buy a new bike and get out there again!
I'm from Sheffield and most of my off road riding would be in the Peak District, though because I don't drive then I'd have to ride out from where I am too. I'm looking towards purchasing a hardtail, as I feel the leap from what I was riding before to a full-sus would be a little OTT, and I need to refresh and redevelop my skills (or lack there of!) Full-sus would be something that I may work up to eventually, but for now I want to be able to feel the terrain and get instant feedback on any mistakes (well, crashes...)
I've been doing some research but I'm now slightly stuck and hoping you guys can give me opinions as to which way I should best look. Most bikes I've seen seem to have 100mm travel, but I've also been advised that I might be better looking at a little more travel than this for peak district riding, perhaps up to 140mm. I was wondering on this - is this right, or would 100mm travel do? Is it just a case of something like I could go faster on rough ground on 140mm than I could on 100mm due to not worrying so much about rocks/bumps hit at speed, or that on the negative it might make me a 'lazier rider' by allowing me to be riding easier lines? If I'm really better off on 140mm travel than 100mm then that's fine, but in the back of my mind I'm then asking myself why a lot of the bike shops seem to stock a majority of 100mm travel bikes? Is it a cost thing or something else? Am I even asking the right questions, and if not then what questions should I be asking, please?
I used to love woodland/open singletrack, descents but not 'downhill' (what I've seen on Youtube like Ben Nevis, that's a little extreme for me! I think my limits might be perhaps a slower more careful descent of Jacobs Ladder after a lot more experience and practice!) I've heard there's trails in Greno Woods and Parkwood springs now, so I'll probably be trying my luck on these at some point.
The three bikes I've shortlisted so far are all 650b as I think a 29er is too big for me and my storage space. I'd be just as happy on a 26er, but they seem to be phasing out now and the benefits of 650b sound good (roll-over pitch and rolling resistance etc.) hopefully I ain't just buying into the marketing as I know 26 is tried and tested over many years...
Option 1 is the Cube Attention 27.5 at £699. This apparently has a 100mm Suntour XCR LO DS fork. I've heard bad things about Suntour and would probably use this until such time as my first upgrade, then go up to some form of air sprung Rockshox (that'll then perhaps be a subsequent question) I figure it'll at least get me going and then I can look at upgrading as-and-when, or would the ride/reliability really be quite bad?
Option 2 is the Scott Aspect 710 at £899. This has the 100mm Rock Shox XC30 TK Solo Air. From checking, it again seems a fairly budget ranged air fork, but again I figure it'll get me going but might hopefully be a better offering than the Suntour on the Cube and last longer before a required upgrade, hence if it's a better ride and better reliability then I'd be willing to pay the little more than the Cube. The price difference on the other would partly be to help pay for the eventual fork upgrade.
If you guys say I'm best off looking at 140mm as opposed to 100mm then I'd look towards
Option 3 is the On-One 45650B Shimano Deore at £899.99.This comes with a tapered Rockshox Sektor RL 140mm Solo Air and a 15mm axle. I figure this is my best bet for the money based on what seems to be quite a good fork and components. Planet X is a little more difficult to get to for me, but 140mm is the way to go then so be it.
And my last potentially stupid newbie question, how much difference is there between a 100mm and 140mm travel geometry for riding on the roads to the trails? Is it do-able or a little stupid?
I'd be purchasing outright, no cycle to work scheme or anything. All of your advice is appreciated, and I thank you for your patience. Sorry that this became a little long.
I'm from Sheffield and most of my off road riding would be in the Peak District, though because I don't drive then I'd have to ride out from where I am too. I'm looking towards purchasing a hardtail, as I feel the leap from what I was riding before to a full-sus would be a little OTT, and I need to refresh and redevelop my skills (or lack there of!) Full-sus would be something that I may work up to eventually, but for now I want to be able to feel the terrain and get instant feedback on any mistakes (well, crashes...)

I've been doing some research but I'm now slightly stuck and hoping you guys can give me opinions as to which way I should best look. Most bikes I've seen seem to have 100mm travel, but I've also been advised that I might be better looking at a little more travel than this for peak district riding, perhaps up to 140mm. I was wondering on this - is this right, or would 100mm travel do? Is it just a case of something like I could go faster on rough ground on 140mm than I could on 100mm due to not worrying so much about rocks/bumps hit at speed, or that on the negative it might make me a 'lazier rider' by allowing me to be riding easier lines? If I'm really better off on 140mm travel than 100mm then that's fine, but in the back of my mind I'm then asking myself why a lot of the bike shops seem to stock a majority of 100mm travel bikes? Is it a cost thing or something else? Am I even asking the right questions, and if not then what questions should I be asking, please?
I used to love woodland/open singletrack, descents but not 'downhill' (what I've seen on Youtube like Ben Nevis, that's a little extreme for me! I think my limits might be perhaps a slower more careful descent of Jacobs Ladder after a lot more experience and practice!) I've heard there's trails in Greno Woods and Parkwood springs now, so I'll probably be trying my luck on these at some point.
The three bikes I've shortlisted so far are all 650b as I think a 29er is too big for me and my storage space. I'd be just as happy on a 26er, but they seem to be phasing out now and the benefits of 650b sound good (roll-over pitch and rolling resistance etc.) hopefully I ain't just buying into the marketing as I know 26 is tried and tested over many years...
Option 1 is the Cube Attention 27.5 at £699. This apparently has a 100mm Suntour XCR LO DS fork. I've heard bad things about Suntour and would probably use this until such time as my first upgrade, then go up to some form of air sprung Rockshox (that'll then perhaps be a subsequent question) I figure it'll at least get me going and then I can look at upgrading as-and-when, or would the ride/reliability really be quite bad?
Option 2 is the Scott Aspect 710 at £899. This has the 100mm Rock Shox XC30 TK Solo Air. From checking, it again seems a fairly budget ranged air fork, but again I figure it'll get me going but might hopefully be a better offering than the Suntour on the Cube and last longer before a required upgrade, hence if it's a better ride and better reliability then I'd be willing to pay the little more than the Cube. The price difference on the other would partly be to help pay for the eventual fork upgrade.
If you guys say I'm best off looking at 140mm as opposed to 100mm then I'd look towards
Option 3 is the On-One 45650B Shimano Deore at £899.99.This comes with a tapered Rockshox Sektor RL 140mm Solo Air and a 15mm axle. I figure this is my best bet for the money based on what seems to be quite a good fork and components. Planet X is a little more difficult to get to for me, but 140mm is the way to go then so be it.
And my last potentially stupid newbie question, how much difference is there between a 100mm and 140mm travel geometry for riding on the roads to the trails? Is it do-able or a little stupid?
I'd be purchasing outright, no cycle to work scheme or anything. All of your advice is appreciated, and I thank you for your patience. Sorry that this became a little long.

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Handbuilt Steel 29er https://goo.gl/RYSbaa
Carbon Stumpjumper https://goo.gl/xJNFcv
Parkwood:http://goo.gl/Gf8xkL
Ribble Gran Fondo https://goo.gl/ZpTFXz
Triban:http://goo.gl/v63FBB
From experience the cube will probably have a quite steep head angle and a much more xc/race focused geometry. I expect the Scott to be similar. The 456 should have a much slacker head angle giving more confidence on the downs.
I'd go with the 456 too.
http://www.halfords.com/webapp/wcs/stor ... yId_165499
The 456 may be faster coming down, but going up.......it's also a lot cheaper than the 456!
No need for a lockout on road if you have a good damper, it wont be bouncing up and down if it has a decent damper anyway!
Parkwood springs looks like a decent little loop. Hoping to get down there at some point for a quick try.
Not sure what part of Sheffield you are from but Eckington woods has some reasonable stuff that will keep you entertained for a few hours.
Thanks for reminding me on that, it was something I was specifically looking for but didn't think this was the major deciding factor? I suppose I was trying to ask about the difference of handling/response between the 100mm and the longer travel, as I understood that 100mm is aimed at XC racing and might be a quicker response (like, how quick it feels of a turning circle etc.), thought that longer travel may equate to slower handling/turning which might be a little crazier in the traffic we have here. I don't think I'm explaining myself well, sorry...
I hadn't considered the Boardman's, partly because the Halfords setup might be hit or miss and that I've previously had more experience with Shimano than Sram, so I was originally thinking that maybe I should stick to what I have more experience of for now, though realise things have still moved on a lot and my experience probably doesn't count for much. Your suggestion made me re-evaluate though and I've been looking at that a little more today and the Boardman Team HT 650B 2014 at £849.99 You mentioned about climbing but the Boardman you listed seems heavier than what I'd previously shortlisted? Or is it also that longer travel makes climbing harder? (I thought that's partly what the damper was for?) Expanding my options is good though, so thanks - I guess I'll have to do more testing of more models in more places than I was initially thinking to!
Could anyone point me in the direction of a quick product comparison matrix on the Avids please, and where in comparison to Shimano/Sram that they'd come in a hierarchy? Like is DB1 more at Alivio or Deore level, or something else? I understand that competing companies mightn't be exactly directly comparable but a rough/best guess would be great if at all possible?
I'm near Endcliffe Park, near Ecclesall Road sort of Hunters Bar/Sharrow but not quite. It's an easy enough ride to the Peaks for me going through the parks/Porter & Mayfield Valley, and if I want to get out there quicker I can always go up Ecclesall then Ringinglow road or go up through Fulwood or Crosspool and up towards Redmires/Rivelin. Eckington is quite a bit of road riding to get to from my end of the city, but I won't discount it just for that - thanks for the tip, I'll have to check it out more once I've actually bought myself a bike. I'd heard that someone got held up for their ride at Parkwood shortly after it opened but I'm unsure how accurate that is and might just be rumour. Knowing that area ain't too far from Pitsmoor and Shirecliffe which can get a little rough then I ain't completely discounting it though and so I'll probably at least try and go up in a group rather than on my own.
Sorry for all the more questions, but I'm still trying to get my head around it all. Thanks again for all the help so far
It shouldnt make a difference, as frames are designed with the travel in mind, are you asking that if the fork has more travel (possibly making it longer) then would the frame be higher which could in turn change the handling? It won't make much difference, most bikes are designed to try and get the handlebars quite low, as more weight on the front wheel means better grip. If its your first proper bike in quite a while then it wont make much difference to you and i wouldnt worry about it too much.
Handbuilt Steel 29er https://goo.gl/RYSbaa
Carbon Stumpjumper https://goo.gl/xJNFcv
Parkwood:http://goo.gl/Gf8xkL
Ribble Gran Fondo https://goo.gl/ZpTFXz
Triban:http://goo.gl/v63FBB
Yes, this will be my first bike purchase in ages - previously coming from rigid with no real experience of bouncy forks so I'm trying to get my head around it. I suppose I was previously thinking partly of the potential wheel base differences too, like short wheel base transit van having different handling than a long wheel base transit because of the extra distance between the wheels, means the long wheel base has a larger turning circle, and seems slower to steer as a consequence. Back to the bike, in my mind the longer travel would put the front wheel further forward so increase the wheel base. Better 'extreme analogy' of my previous thought process might be a Harley vs a sports bike(?) thinking of the front end that is... It was also partly the whole front end raising thing, though you've already corrected me on that. I've since been trying to do reading on bike geometries, but there's lots of stuff out there and I figure I'm just better to go out and test ride some stuff now and see what 'feels right'.
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I've got a 456 evo that is a couple of years old. I ran it at 150mm travel for ages then recently dropped the travel to 130, it climbs much better now and I haven't missed the 20mm.
Do we ever do Sheffield ride outs? There's a massive thread in the rides area started back in 2009 for rides out of Hull thats still active. Seems there's quite a few people around Sheffield, at least if this small thread is anything to go by! I'd be up for a mixed ride out with anyone once I get a bike sorted but I'd probably end up slowing others down, at least in the short term.