Amazon is selling "The Simpsons Game" for £9.96 + £1.69 P&P = £11.95.
Alternatively, if happen to be going to PC World, or fancy giving them a ring then they have this game listed on their site at £29.98. Using their Price Promise, you can get 10% of the difference back, making this just £10.15.
The next best price is £14.99 from PowerPlayDirect.
In The Simpsons Game, Homer, Marge, Bart, and Lisa use exciting, all-new powers to save the world from rising chaos. To help the Simpsons, gamers at home must journey through all of Springfield (as well as vast worlds beyond), vanquish an amazing array of villains, and fight their way through parodies of multiple popular games.