Seen as how DDR2 prices have gone through the roof recently, I think this is a decent price, 1GB of DDR2 Kingston Value RAM costs £17.99 on Play. http://www.play.com/PC/PCs/4-/3274794/Kingston-KVR667D2N5-1G-Valueram-Computer-Memory-1GB-PC5300-DDR2-667MHz-240-Pin-Dimm/Product.html
(If you use the Zavvi code APRIL2 you can have 2 *1GB sticks for £23.92 Delivered) £11.96 each. £2 off a £20 spend with code: APRIL2
ValueRAM is Kingston's value-priced line of industry-standard, generic memory intended for customers who have white box or generic computer systems, or who plan to purchase memory by specification. ValueRAM is designed to industry specifications tested, is 100% tested and is available at competitively low prices.
Manufacturer Warranty: Limited lifetime warranty
Miniscule 2% Quidco, but every little helps :)