In your price range then the Spesh or the boardman are quality bikes. I have a sub for What mountain bike and they rate the Carrera Fury as the number one starter mtb bike for your price range And also the voodoo Hoodoo (£500) is rated higher than the spesh.
I also wouldn't rule out this from Canyon http://www.canyon.com/_uk/mountainbikes/bike.html?b=2537
Or if you could stretch the budget a bit this from Planet x http://www.on-one.co.uk/i/q/FBOOINX529/on_one_inbred_x5_29er_bike
I'd also look at this Giant which has a great spec on it http://www.edinburghbicycle.com/products/giant-revel-ltd-0-12
I also wouldn't rule out this from Canyon http://www.canyon.com/_uk/mountainbikes/bike.html?b=2537
Or if you could stretch the budget a bit this from Planet x http://www.on-one.co.uk/i/q/FBOOINX529/on_one_inbred_x5_29er_bike
I'd also look at this Giant which has a great spec on it http://www.edinburghbicycle.com/products/giant-revel-ltd-0-12




