OK, so this may not work in every store but worth a mention as it worked for me...
Basically the game is priced up at £39.99 and I assume that's the in store price for GAME ONLY. I asked how much the guitar bundle was, and the spotty kid who works there told me £39.99. I didn't then ask too many questions, just gave my money said please and thank-you at the right time and ran like the wind!
This was in the Trafford Centre this morning, the store was ultra-busy, the spotty kid looked extra-clueless and I capitalised on that with a great deal. Like I say, may not work for you all, just try being in the right place at the right time!