I was having a look on the net and saw this site to buy the MB, Memory and CPU and wondered if these match ok:
AMD Athlon64 3200+ Socket 939 (Venice) CPU -Retail Box- £84.95
Corsair Value Select 1024Mb DDR400 KIT (2x 512Mb) Memory £49.95
GigaByte K8NSC S939, AGP, GBLan, 5.1Snd, ATX £39.95
Total about £205
Might need a new PSU though but will try that when i get there.
The only thing i was looking for a 3Ghz CPU but they are not quite in my price range at the moment unless i spend a bit more to get the better chip as should last a few years.
These are from Eclipse Computers
I could not see any 3Ghz Athlon Chips there but the oen above should be fast enough.