AMD Athlon II X4 635 http://www.ebuyer.com/product/191956
ASUS M4A89GTD PRO/USB3 http://www.ebuyer.com/product/198314
Crucial 4GB (2x2GB) DDR3 1333MHz/PC3-10600 Ballistix Memory Kit CL7 (7-7-7-24) 1.65V http://www.ebuyer.com/product/179278
£95 - The good set of 1600mhz G.Skill is getting very expensive.
HIS HD 5770 1GB http://www.ebuyer.com/product/186468
ATI is the better option atm. It requires less power, so a less expensive power supply will more easily do two of them. There are more AMD motherboards that support crossfire compared to SLI. Performance is better for the money as well.
OCZ Z Series 650W 80plus Silver http://www.ebuyer.com/product/141006
Windows 7 64-bit Home Premium http://www.ebuyer.com/product/173791
I wasn't clear whether you needed an OS or not so I included one anyway. If you don't then you will be able to do a much nicer build.
I would probably spend the spare £25 on getting a Phenom II X3 or X4.
If you have to have Nvidia, then change to a GTX260 (~£160), and get this motherboard so that you can SLI: http://www.ebuyer.com/product/173986
£80 but you would need a 750W PSU to have enough power to SLI two of them.