Long time reader, first time poster - go easy on me.
Granger Games currently have Far Cry 2 as their Deal of the Week for £5
Game currently have an offer whereby if you trade in Far Cry 2 (or GTA IV or Battlefield Bad Company or Splinter Cell Double Agent), you can get the COD:MW2 Resugence Pack for 99p. More info here http://www.hotukdeals.com/item/687948/1200-microsoft-xbox-360-live-points
(For anyone unfamilar the resurgence pack is basically 1200 Microsoft point you credit onto your account with the intention of purchasing the DLC of the same name, though it can be used for anything - this typically fetches £9.99).
So I just picked up a 2nd hand copy of Far Cry 2 for £5 from Granger Games, walked outside, took the price stickers off, then walked 50 yards down the road to Game where I traded it in and paid 99p for 1200 Microsoft Points! :D
These were both in my local Redcar branches, I'm unsure if it's nationwide or not, and I believe the offer runs until the 17th of June.
Reciept URL: http://img101.imageshack.us/img101/9264/dsc00100rb.jpg