Tesco are now selling the Nintendo Wii U Pro Controller Black for £34 (the same price as Amazon). But If you use code TDX-HQ9T you can save £5 (Conditions for the code is a £30 minimum order value). Please note, this code only works for new customers and you have to be quick, code expires on 30-06-2014.
You can also get some cash back on this from either Quidco or TopCashBack.
Free delivery as well if you choose delivery to a store.