Unless there is a real need for wireless, I would get myself a cable router and two Homeplug devices. Attach the cable modem to the router (ethernet), then the router to one Homeplug device. The other Homeplug device can be put into any electric socket in your home, and will provide the ethernet link to your computer.
For the Homeplug devices, this company are UK-based and have excellent customer support:
http://www.solwise.co.uk/net-powerline.htm