Amazon have Rock Band up for preorder for £69.99. This is probably a misprice as the game is up for preorder in the US for $200.
The bundle is likely to consist of the following:
The Game itself
A Drum set
Wireless Fender Guitar
Now it doesn't say whether it is the bundle, however it's priced too high to be the game only. Remember, Guitar Hero II on the 360 cost the same amount just including one guitar!
It's definitely a misprice and worth preordering just in case they honour it. My guess is that this won't be cheaper than £100 here when it's released.