I was in HMV today and found Rock Band (Game Only) for PS3 included in the 2 for £30 deal (or £19.99 each). Other games in the deal
Updated with photo of the shelf, if you look carefully you can see the xbox shelves in the background (they had more choice of course!)
Battlefield Bad Company
Race Driver Grid
The Orange Box
They also had Star Wars Force Unleashed when I went in the first time but that was no longer available the second time. There was a guy there stacking the shelves as I left so they may have had a some others.
Their online price is still showing as £39.99 but this was definitely available in store,