How about this:
Intel Core 2 Quad Pro Q6600 "Energy Efficient SLACR 95W Edition" 2.40GHz (1066FSB) - Retail
Asus P5Q Pro Intel P45 (Socket 775) PCI-Express DDR2 Motherboard
Corsair 4GB DDR2 XMS2 PC2-6400C5 TwinX (2x2GB)
HIS ATI Radeon HD 4850 512MB GDDR3 TV-Out/Dual DVI/HDMI (PCI-Express) - Retail
Western Digital Caviar Blue 640GB SATA-II 16MB Cache - OEM (WD6400AAKS)
Corsair HX 520W ATX2.2 Modular SLI Compliant PSU (CMPSU-520HXUK)
Samsung SH-S223F/BEBE 22x DVD±RW SATA Dual Layer ReWriter (Black) - OEM
Antec 300 Three Hundred Ultimate Gaming Case - Black (No PSU)
Total slightly over £600 at £603.87 + shipping.
There is also space for another 3 120mm fans, it comes it top and rear. Also could add a better cpu cooler so you could overclock the Q6600, such as the Arctic Cooling Freezer 7 Pro CPU Cooler (Socket LGA775) at £18.39.