Cheapest I could find next best is
Game.co.uk 34.99 (+quidco and reward)
or hut 34.99 (+10%)
Xbox 360 Wireless Headset - Wireless freedom, comfort, and superior voice quality.
This stylish and lightweight Xbox 360 Wireless Headset seamlessly integrates with the Xbox 360 to complete your wireless experience on Xbox Live.
-Enhanced audio/voice quality over Xbox Live
-Removable ear grips with 2 size options for maximum comfort and stability
-Communicate wirelessly with up to 30ft. range