Also available at DVD.co.uk for £9.95 (they seem like the same company) and on Play Trade for £9.99. And BlahDVD for £9.87.
I only bought this last week for £15 and not even opened it yet. It's sold out in most other places and the game itself is about £20 else where.
The Dancing Stage has sold over two million copies in Europe to date and the latest instalment, Dancing Stage Supernova 2, is the biggest yet. It features a brand new Hyper Master Mode, in which you must complete a series of stages before going up against a boss in a classic dance off.