Belkin - I don't allow 'em in the house any more after several problems with 'em and a total lack of interest from "customer service". They nearly work.
Tony - if you can get your hands on a wireless device for him to try, I would. I live in a 15th Century house and the WiFi covers the whole place.
Failing that, you're into running cables. You can get Cat 5 cable in almost any length (or even make up your own if you have the right cable stock). I had a 10 metre one from my study to the attic in the old house, with a backup server up there, and it worked fine. It's twisted pair stuff, not coaxial. I've never dug inside one (they're so cheap it ain't worth the bovver) but I think there are three twisted pairs.