I could be wrong, but I think Halfords can order virtually any bike for you under the cycle to work scheme.
Personally I don't see the point in having any kind of mountain bike when you'll be sticking to the roads 99.9% of the time, a hybrid or full out road bike is the way to go, but if your after a hardtail then the Focus bikes at Wiggle are great value (http://www.wiggle.co.uk/p/Cycle/7/Focus_Fat_Boy_2009/5360037565/) free postage and they do the cycle to work scheme, is £50 over your budget but worth the extra I think.Dom
good bike if you live in a flat areahttp://www.cotic.co.uk/product/simple
Presumably there's a whole load of sarcasm in that post Chappers?