Bit of a fluke finding this one.. I was trading in a few games at GameStation and buying Medal of Honor for £39.99 as I hadn't pre-ordered it.. Anyway, next to medal of Honor was a sign saying you could buy a used copy of Mass Effect 2 with Medal of Honor for £4.99.. However, I was trading in Mass Effect 2 so it was of no interest to me, but having checked my receipt, I got £13.00 trade-in for the game..
As such, if you have a copy of Mass Effect 2 and you want Medal of Honor, take it with you, trade it in for £13 bringing the price of MoH down to £26.99, then buy a copy back for £4.99 bringing your total spend to £31.98.. Comes with Battlefield Beta Invitation too..
Bit long winded maybe, and kinda dependant on you having the game, but still a fair deal if convenient.. I'd do it today though, the guys on the counter reckoned the system would update over night and put the trade-in on mass effect down to £8.