I've just quoted a price of 710 ukp for a system very similar to that.
AMD 64 3500+ 939
Don't remember the motherboard, I think Asus. gig lan etc.
1 gig 400 RAM (crucial)
9800pro GFX
160gb SATA HD
Good mouse
Good keyboard
It was just the box though, no OS or moniter, which add a lot to the price. I'm also advising to wait until PCI-Express boards become available.
Oh, and I buy from eBuyer and cclcomputers generally.
edit : And that included 17.5% VAT too... the price without that was a lot less.