Spotted this on the shelves of Currys Coventry yesterday for their new store opening. It's just the solus game, no instruments included.
They had two left on the shelves, didn't pick one up as I don't have time to play the Wii lately!
I had the sales assistant scan the game and it came up at £4.97, so presumably a nationwide deal if your local has stock :)
The Coventry store was on Airport retail park (formerly Orchard retail park)
I believe they are also doing 10% off this weekend for the new launch