Which bike?

You have to factor in the type of riding you are planning to do and also your size. A light bike will benefit you so I guess 27.5" has to be the wheel size. I

think the bikes you have listed are good options but I can't help wondering if going for a cheaper bike that allows you to put a much better fork on it with your spare cash might be the best option. I thought this deal was quite good and is only available in limited frame sizes but those suit you.

https://www.cyclerepublic.com/saracen-m ... -2018.html

It leaves you with spare cash for a fork upgrade and don't forget you will be able to sell on the existing fork as new.

If you haven't had a decent mountain bike before you really want to get out and see some bikes instore and get a feel for what you want. Halfords, local bike shops anywhere really where you can start getting an understanding of what you like and dislike. Yes you won't be able to get the full picture without riding it but it will give you a better grounding. I definitely think you are on the right track considering heavily discounted bikes even 2017 models that will maximise the value you get. The £ has dropped in value and some of the bikes a couple years ago were better value anyway and then to have extra discount added too. It doesn't always pay to have the latest model.

Enjoy the shopping experience and take your time unless there is an offer to good to miss of course.

Don't forget that when you buy the bike you may want to customise it to suit you fairly soon so budget for that. Don't spend all your money on the bike and then have nothing left to spend.