Probably the Geforce 6600 GT, and would be exactly that price, and maybe 10 quid cheaper by some makes.
Thats definetly the best card for that money and will run new games easily, though not at the top resoloution and at top settings.
Though will easily run games at 1,028x 1,024 with 2x AA (smoothing filter) and 2x AF ( texture sharpness filter) and still giving around 50-60FPS+ in new games
The XFX Gefroce 6600 GT Extreme Gamer Edition is a great version of the card, is already overclocked, and can be overclocked more using the software.
It costs about £145