Solve your storage problems with a Western Digital 2TB My Book USB 3.0 External Hard Drive for £55 from Tesco. Click here to buy >>
Need something for housing your rapidly-expanding Steam library? Or perhaps you're getting into game capturing and need somewhere to store your video files? Whatever the reason, Tesco have slashed their price for the Western Digital 2TB My Book USB 3.0 External Hard Drive (thanks to nickc74 for the tip!). It's mains powered, so it should work with Wii U consoles as well, and Nintendo lists the MyBook range amongst compatible units.
It's worth noting that you don't necessarily need a mains-powered HDD for the Wii U. I prised the hard drive out of my defunct, 8-year-old laptop and used a Y-cable and it works perfectly.