is who i like, some others had bad experiences with them. A pound is worth two dollars, but expect ~40-50% price increase like for like here.
Cutting corners massively:
Abit KN9S nForce 550 (Socket AM2) PCI-Express DDR2 Motherboard £52
Maybe be able to save RAM (free) (2GB will cost 150+)
AMD Athlon 64 X2 Dual Core 3800+ 2.00GHz (Socket AM2) - Retail £88
Antec NeoHE 500W Modular ATX2.0 PSU £62
HIS ATI Radeon X1950 Pro ICEQ 3 TURBO SILENT Heatpipe 256MB GDDR3 VIVO £135
Thats around £330 without mouse / keyboard - no idea if it will work together, but should do. What do you have for hard disks?
Actually quite tempted to get that vidcard myself.
Eck, forgot VAT - add 17.5% to that price - do you know anyone with a business? Cant really go much lower than that without it being pointless to upgrade. Maybe knock 50 quid off with a single core AMD, and another 50 quid off with a budget graphics card - like a ATI 1600 or something.
How old are you? Should be able to make the extra costs fairly easily by working/paper rounds/ebay/protection racket/selling soul to satan etc.