Online its £17.99, yet for only £2 more, you can get the deluxe edition that comes with a nice cardboard box, a Metallica/Guitar Hero T-Shirt and some Art Cards.
Great price, especially for instore. The normal edition is the same price aswell. Didnt see any 360 versions but there maybe.
This was found in London (oxford street store) today, and they still had a few left.