Thought I'd post this as lots of people were unable to get it when it was £3 at Tesco recently. This deal is obviously in stock at the time of writing and it's still a decent price.
Opinion seems to vary, but you may or may not be able to use the one month Gold code included to add on to your 360 Live subs. I'll await confirmation on that one way or another.
Besides that, I'm sure you all know what this game is!!
Next best price (in stock) is £9.95 at Games4U.