John Lewis are selling "Super Paper Mario" for the Nintendo Wii for £19.99 (inc Del)
You can get cashback from the usual sites (e.g. 3% Quidco, making it just £19.35)
The next best delivered price seems to be £24.99 from ShopTo.
You can also get it 'Collect from Store' from Comet for £19.99.
Prepare to enter a whole new dimension with Super Paper Mario on Wii! The planets favourite plumber returns in the third Paper Mario game, bringing a different perspective to the series as he calls on old friends and foes to help him tackle a mysterious enemy from a bizarre parallel universe. Lead Mario in his quest to overthrow the evil Count Bleck before he succeeds in creating a Chaos Heart and bringing about the end of the world as we know it, playing as Luigi, Princess Peach and Bowser along the way as you free them from captivity.