Corsair

Crucial is good.. but you won't get a major overclock.
Geil

(utter tripe, the sort of things OEM's will try to give you)
TwinMos is similar to Crucial, I've used it myself a few times.
My choice.. or something similar
http://komplett.co.uk/k/ki.asp?sku=302393&cks=PRL
I doubt you'd get XMS for £150.