im a very mountain biker and quite in the know with regards to parts and bikes as well as lots of leisure lakes contacts.
if your serious about getting into the sport then you need to decide on the type of riding you do or want to do. so many people pick the wrong type bike for the wrong thing, with a bike that has totally the wrong geometry and it spoils their riding style and ruins confidence.
but if your just wanting to commute then you should be looking at a comfortable road cruising bike, relaxed geometry, not too small, not agressive.
most bikes in that price range will be very similarly equiped in terms of parts, and most will use their own branded parts along side OE aftermarket parts. Nowadays bikes seem to be getting lower spec'd each year, but across a certain price range are very similar.
best thing i would advise is get a sale deal, or even a second hand deal. some people hardly use a bike when they buy one so some second hands are literally like brand new. meaning you get a £1000 spec'd bike for easily half that, giving you a spec beyond what you couldve afforded brand new
sadly to get a bike that really is top notch, with very good spec, your looking at easily over £1500 now days. parts and bikes have gone way way up in price over the past couple of years. for example, a set of fox 36 rlc forks would once have cost you £5-600, now they are near £1000. it really has become silly.