erm theres no point in getting a SLI board especially one with 32x PCI-Express (gimic) when u want a ATI card.
Im a fellow UK'r, so il help u anyway i can, you need to find out what PSU you have, and tell us wat the AMPS are and all the other necessary specifications.
For the Video card, i have the X1900XT which is best value, you can OC it up to X1900XTX speed easily, so get XT.
For motherboard id get DFI lanparty Ultra-D.
and for CPU id get Opteron 165 Dual core.
Id probably get a new case depending on what yours is.