I recently purchased a Dell XPS 1710 from this site for £510.
2.16 Ghz C2D
2 GB DDR2 Ram
100 GB 7200 RPM Hard drive
Looking at the site they seem to have quite a few back in stock..
These laptops do not come with operating systems and only have 90 days warranty although mine came looking pretty much new in a Dell box.
Quidco also available