Xbox 360 Wireless Bridge £46.96 at Amazon with free supersaver deilvery.
* Play head-to-head wirelessly on Xbox Live, or on your home network
* Dual band 5 GHz and 2.4 GHz Wireless A/B/G home network compatible
* Compact, high performance design
* Powered by Xbox 360 to eliminate adaptor clutter
* Streams photos and music from Microsoft Windows XP
* Plays recorded TV, movies and videos from your Microsoft Windows XP Media Center based PC
* Easy setup and installation
* Collaborates with Xbox 360 authentic wireless accessories for worry-free integration
* 802.11a allows stepped-up data
Still overpriced but the cheapest I've seen it.