Back down to £15.99 at Bee.com, seems to be the current cheapest as Amazon price has gone back up to £17.35
"Just Dance has got America dancing! The #1 Best Selling Music/Rhythm Game on the Nintendo Wii system is back to keep the party going with an all-star track list, the hottest dance moves of today, and a brand new beat for everyone to enjoy. Just Dance 2 features over 45 new tracks from classic hits and legendary songs to today’s chart-toppers. This time, you can create your own dance crew and compete against others in a true dance off across a variety of play modes, including the new Dance Off and Party Mode."