Have a look on here for some bikes.

The Cube Acid looks good for the price.

http://www.chainreactioncycles.com/C...ategoryID=1890

But thats at the top of your budget.

Discounted Trek..

http://www.evanscycles.com/products/...heel--ec020798

Gary Fisher, albeit has cable disc brakes which are not that good but they are an easy riding bike.

http://www.evanscycles.com/products/...812?query=gary fisher