Looking at getting a MTB. Not sure if hardtail or full sus. Want to do trails. Budget £2000
If you are a beginner I would recommend spending much less to start with. I know few people who bought a very nice bike but it just sits rusting in their garage and not being used all depends if you get into the sport etc. If you are keen though there are many nice options... Its always nice to test ride the bike first and also have a rough idea what you will be riding. For example for cross country a short travel 100mm hard tail might work better however for £2000 you can also get an excellent cross country full sus. If you are looking for a bit of everything like trail centres and cross country rides and big days out on the mountain look for 130-140mm bikes, personally I wouldn't bother with enduro 160mm bikes unless you are interested in just trail centres or focus on downhill stuff as these can get heavy and less efficient when pedalling but then again there are always exceptions... my mate rides his 170mm YT Capra on XC rides and climbs faster then me when I ride my 130mm Boardman.
Take a look at for mid travel full sus bikes Bird Aeris, Giant Trance, Canyon Spectral, Vitus Escarpe, Whyte T130, Commencal Meta TR 4.2 these generally get very good reviews.
For mid travel hard tails take a look at Vitus Sentiner or similar bikes, the Vitus comes in 27.5 and 29er and you can pick one for £700-£900 depending on the spec and use the spare cash buy a dropper as well.
Have a look at what your mates ride too as you will likely be spending most of your time riding with them and might be worth riding similar type bikes so you could keep up with their pace.
I've just bought the 2017 Giant Trance 2 for £1,550 (reduced from £2,399). Absolutely superb bike. I've previously owned two Turners (5.Spot and Flux), a Norco Sight, a Vitus Sommet and a clutch of hardtails and this is the best bike I've ridden bar none. Took it round one of my local(ish) loops in the North of England yesterday. Mix of fast , rocky descents and very steep, rubbly, rocky, rooty technical stuff, all covered with moss and over 800m of climbing, of which mainly track but bits of steep technical thrown in. Handled everything with aplomb. Never felt more in control (and this despite the long stem/narrow bar - which I will swap out - that it comes with). Pedals well, handles brilliantly and copes with stuff that my 160mm Sommet struggled with. Highly recommended.
For balance I also spent half a day on a Bird Aerie 120. Lovely bike but very long and low stack and after 2 hours my shoulders and neck were killing me, so I decided against that.
My first bike I didn't like so ended up getting a different one. Second time around I test rode a few to make sure I was 100% on what I wanted.
Titus El Chulo 27.5 | 2017
Trek Slash 9 27.5 | 2015 (building)
I bought a Scott Genius MC-10 after I tried one out at Glentress, and I've never regretted buying it.
I'm with the above, try a few bikes to see what YOU prefer for where YOU will be riding.
Giant still do their 'test ride' program, will give you a chance to try some different types of bike out https://www.test-ride.co.uk/
obviously you don't have to buy a Giant!
Push it to £2.5K and you can get a half price Intense Tracer this week depending if its your size.
I'm guessing you're going to want an enduro type bike rather than a XC one so 140-160mm travel.
A carbon frame if you can look after it and not get it gouged out - so there's also Stumpjumper Experts at £2.5, a Mondraker Foxy R at £2.3 or a Kona Process 152 at £2.2.
There's soooo many good bikes at just over £2K you will be spoilt for choice if you catch them in the sales. Pretty sure I saw a Trek Remedy 9.7 recently that nearly fits your budget.
Anyway get some rides in as the others have said and get an idea for the sort of geometry you want and what feels right. Then take a look here and see if you can find it anywhere in your budget