Not sure why anyone would spend £200 on a 5850 any more, when you can get a 6870 for the same, or a 470 for less??
Intel build making maximum abuse of this-week offers

. i5 is more powerful than phenom II, has fast C7 RAM, decent cooler for your 4GHz overclock, new 6870 GPU, Bluray drive (remove if you dont want Bluray)...
HIS ATI Radeon HD 6870 1024MB GDDR5 PCI-Express Graphics Card with FREE CODMW2 PC-Game £199.99
Intel Core i5 760 2.80GHz (Lynnfield) (Socket LGA1156) - Retail £138.64
Gigabyte GA-P55-USB3 Intel P55 (Socket 1156) DDR3 Motherboard £88.11
*** PROMO *** OCZ ModXStream Pro 700w Silent SLI Certified Modular Power Supply £58.99
Patriot Viper 4GB (2x2GB) DDR3 PC3-12800C7 1600MHz Dual Channel Kit (PVS34G1600LLK) £57.99
Samsung SH-B083L/RSBP 8x BluRay ROM / 16x DVD±RW Drive - Black (Retail) £46.99
Coolermaster Elite 430 Case - Black £41.99
Samsung SpinPoint F3 500GB SATA-II 16MB Cache - OEM (HD502HJ) £33.98
Akasa AK-CCX-4001HP Nero S Direct Contact Heatpipe CPU Cooler (Socket AM2 / AM2+ / AM3 / LGA775 / LGA1156 / LGA1366 ) £29.99
Sub Total : £592.90
Shipping cost assumes delivery to UK Mainland with:
DPD Next Day Parcel
(This can be changed during checkout) Shipping : £10.50
VAT is being charged at 17.50% VAT : £105.60
Total : £709.00