In reply to iain abernethy: Deff try them all out befor you buy one, no point in buyin a bike that looks good and people recomend if it isn't comfortable and dosn't feel good to ride, if your doin xc in it you'll prob be in the saddle for long periods of time.
Always look at the 3 points of contact this goes for any bike
1. Pedals, large surface area and thin is better, as long as they feel comfortable for you.
2. Seat, Firm, made of somthing durable, leather takes longer to wear in but lasts longer and is more comfortable when it is worn in. Get the mech to adjust the seat befor you test it, you should have a slight bend at your knee when ur foot is at the bottom of the rotation.
3. Handle bars and grips, you dont wana be reaching out for them or have them real close near your knees, grips just want to be comfortable and get the Mech at the shop to move the brake leavers and gear leavers so they are in reach befor you test ride.
Also check the length of the frame (top tube) as this is goin to make a big difference to comfort, too long and ur back and arms will ache from reaching, too short and you will have all sorts of problems and back ache. Stand over the bike and make sure you got pleanty of room for the family jewls and then some.
Folks are to taste and situation, Roxshox and Marzzochi are best quality and eastest to look after and get parts for, any others just put the front brake on hard and push down with all ur weight and see wot happens if they feel plush and come back up nice and quick they will prob do nicely. If they bottom out (make a thud when they are compressed) or top out ( make a thud when they come back up) or feel kind of stiff and juddery and slow they not much use cos thats what they will do when you hit something big and thats really not what you want.
Last off, how good are the components the brakes and gears first.
Brakes, good V-brakes are way better than crap cable discs, hydros might be hard to come by for £400.
Gears, Shimano and Shram are the best two, not much between them they just work in a different way to each other. Shram chains are easyer to install/maintain though.
Then the wheels hubs and other moving parts (head set, cranks etc.) then the finishing kit (bars, stem, seat post) then how goos does it look colour etc.
Check out 'Charge' and 'Mongoose' bikes in your price range from Evans Cycles. From the list you picked I'd also go for the Specialized Hardrock try goin for the next model up with hydro brakes if you squeze it it will be well worth it.
Or if you wana go mad I've seen a Commencial Meta 5.5 full sus for about £650 in Sherwood Pines Cycles in Nottinghamshire, she is a Beautiful machine!
Dont know why I just typed all that, it just came out. Hope it helps in some way, Si