Was just browsing Zavvi at everything Xbox 360 orientated and spotted this, cheapest I've ever seen it.
I don't know if it's available instore at this price or not.
Recharge your Xbox 360 Wireless Controller while you play and kiss disposable batteries goodbye! Complete with a charging cable and rechargeable battery pack, the Xbox 360 Play and Charge Kit is all you need to juice up your Xbox 360 Wireless Controllereven in the midst of battle.
* Play & Charge Cable enables continuous gameplay
* More than 30 hours of play per charge
* Battery fuel gauge through the Xbox 360 dashboard
* Includes Play & Charge Cable and NiMH rechargeable battery pack