It simply state that on the motherboard specs (the website you are looking at) or if you go to the store, it will tell you on the package.
Looks like you have around 730 US dollars to spend on CPU, graphics, and motherboard. I'm sure you don't need the SLi mode too so here's a simple, yet a great performer setup:
MSI K8N Neo4 Platinum Socket 939 NVIDIA nForce4 Ultra ATX AMD Motherboard - Retail
AMD Athlon 64 3200+ Venice 1GHz FSB 512KB L2 Cache Socket 939 Processor - Retail
BFG Tech BFGR68256GTOCX Geforce 6800GT 256MB 256-bit GDDR3 PCI Express x16 Video Card - Retail
Total price= $625 USD which equals around 343 British Pounds
Or you know what you can do is get this badass video card and it comes with a free PCI-e SLi motherboard:
Free SLI Motherboard and Fast VGA!
eVGA 256-P2-N528-AX Geforce 7800GTX 256MB 256-bit GDDR3 VIVO PCI Express x16 Video Card - Retail