http://www.ebuyer.com/product/133709 £40.61 (£119.39 left)
http://www.ebuyer.com/product/152177 £103.98 (£15.41 left)

or you could get this ram:

http://www.ebuyer.com/product/146051
http://www.ebuyer.com/product/143844
http://www.ebuyer.com/product/149202

etc.

if you could get a bit more cash then i'd recommend the core 2 quad q8200

http://www.ebuyer.com/product/148933

£133 plus about 40 quid for memory.