Wife and I bought one two years ago on an Asda promotion. I think we used it around five or six times in the first few days. It's been gathering dust since. But thanks for jogging my memory - I keep forgetting to put it on eBay. ;-)
Wii can be picked up quite cheaply but you may also want to consider the Xbox 360 with Kinect. This is the only system that has full body tracking - the others just see the control you are holding. Kinect Sports 1 and 2 are very good with Dance Central 1 and 2 being commonly regarded as the best dance games out there because of the full body tracking.