Coast to coast

I did the whitehaven to newcastle route a year ago on a 10 year old giant hard tail with no prob s, remember your only doing up to 60 miles over an entire day and even with the big hills of which there are lots ,with the time available to you you should be OK. why is it taking you 4 days most do it over 2 or 3 it's only 135 ish miles depending on route?

I do it once a year.
I've been with people who have done it on less training than you, so you should be ok (but they didn't find it easy). I would suggest ramping up the miles between now and then. 30 miles will be ok, and I would also start doing a few hills. There are a couple of longish and steep climbs (nothing impossible, but you will be on your granny cog).

4 days is easily long enough, but doing 50 miles a day would suggest to me that it is more likely be 3 days (4 nights).
I would also check the route you will be taking and check the conditions before hand. Last year we all used semi-slicks or even slicks on the route for a bit of more speed.

So you are doing the Coast-2-Coast + a bit more. Have you got a list of your starting points for each day?
The split for each day will be different - I doubt you will be doing 50 miles each day. You will probably be doing shorter distances on days when you hit the hills. You'll still be on the bike for as long - just that you will be going up rather than along.
But it is still doable if you take it easy and make sure that you are fuelled properly (lots of water, energy gels/flapjacks and a couple of stops for lunch/snacks).
Don't give up on the hills - for me, it's mind over matter. Get into the granny cog on the hills and pootle up (even if it's at walking pace) - it's not a speed/fitness test. As long as you are with like-minded people (looking for a good ride with friends), you will be ok.

Where are you based? Are their any longish hills that you can have a run at just to get your head in the right place? I always find that a couple of weekends hitting a steep hill gives me the confidence that I can actually ride the bloody things.

Are you doing the Coast-to-Coast or the C-2-C..two very different rides.The Coast-to-Coast(Wainrights-StBees Head-Robin Hoods Bay) is almost entirely off road and the C-2-C(Whitehaven-Sunderland) is on green lanes/minor roads etc.If it's the C-2-C then 4 days is probably about right,If it's the Coast-to-Coast then I think 4 days would be seriously pushing it unless you are very fit.