GRAW - £14.99 at Gameplay
GRAW2 - £34.99 at Gameplay
GRAW2 (limited edition) - £34.98 at Amazon.co.uk
Next cheapest I've seen GRAW2 was around £37-£38.
I've seen GRAW1 from around £22 to £30, depending on if it's the "Classic" (budget re-release) , "BAFTA Game of the Year Edition", "Premium Edition", or just the original edition.