This was posted about a week ago herehttp://www.hotukdeals.com/item/329863/guitar-hero-3-legends-of-rock-wth-g/
At the time it was only available in a few stores, not including Weston Super Mare, where it was £50. It looks like the deal has spread to more stores as I picked this up for £24.99 in Weston PC World, where it was £50 yesterday.
I'm reposting because the deal has been extended to more stores. Sorry if that's not allowed, first post!