Which Hardtail

Needabike

http://www.wiggle.co.uk/p/Cycle/7/Felt_Q220_2008/5360032858/
http://www.chainreactioncycles.com/Models.aspx?ModelID=14965

Seeing as I am a roadie can you MTB folk advise me which one is the best value for money

concussion

Out of those two, the BeOne.
Not much in it, but the BeOne has the benefit of a good reputation, a better fork and a better price. Slightly better components but both bikes are pretty similar.
As for the fit, for MTB a smaller frame is better - more room to move over your bike, stiffer rear triangle. I'm 6' 1" and I have a 17" frame, just get an extra long seat tube (think mine is 400mm long) and you have the height for a full pedal stroke when you need it for climbs/non tech stuff. Simply drop the saddle for technical stuff.

Looking at the components, you could expect to have to replace your drivetrain within about two years. If you have a bit of extra dosh if might be worth while upgrading your brakes after a few months, depending on how hard your using it ie if you're pushing yourself and need better stopping power.
Shimano LX Deore hydraulic discs are cheap (under €55 each in the sale right now) and have good power. Only thing is you'll need to get disc hubs too.

Needabike

Took the plunge and got the Beone today

thanks for the advice