ChoicesUK are selling "Bionicle Heroes" for the Nintendo Wii for £7.99 (inc Del.)
You can get cashback through the usual sites (e.g. 5% Quidco, making it £7.59)
The next best prices seems to be £12.93 from The Hut.
The Official Bionicle Video Game: Unleash the power of Bionicle Heroes!
-Play as the heroic Toa or villainous Piraka
-Confront all your favourite Bionicle enemies, past and present
-Explore and battle your way through the exciting jungles, volcanoes and deserts of Voya Nui
-Master the unique elemental weapons and abilities of each character: walk on fire, water...and more!