Revised again. I've changed the case and the DVD drive.
Processor: Intel Core 2 Duo E8400 3GHz £129.95
Motherboard: Gigabyte GA-P35-DS3 iP35 £63.16
Memory: Corsair 4GB Kit (2x2GB) DDR2 800MHz £64.39
Graphics Card: Point Of View 8800GT 512MB £119.98
Hard Drive: Already got (Seagate Barracuda 500GB SATA 7200.9) £0
DVD/CD Drive: Optiarc AD-7200S 20X DVD±RW £15.95
Power Supply: OCZ StealthXStream 600W PSU £47.58
Operating System: Microsoft Windows Vista Home Premium £62.96
Cooling Fan: Arctic Cooling AC-FRZ-7P £15.24
Case: I-Cute Black UL01 Mid Tower Case £20.99
Front Case Fan: Hiper 120mm Case Fan £5.99
Rear Case Fan: AKASA 80mm Amber series 3 pin £3.99
Total: £550.18
So, what does everyone think?