Any ideas what caused it to work, Ian? You said it was an Atheros chipset and you tried madwifi.
No real idea. Ubuntu did claim it had proprietary drivers for the Atheros chipset but they didn't work. Mortal command line combat with Madwifi did offer a momentary glimpse of next door's Sky box (though not my network, conclusive proof that Murdoch is the devil and can reach into your very brain if he wanted to). Momentary, because it never worked again. I think it was trying to get me excited before stealing victory from me at the last minute.
I did some Googlenoodling of Linux and Hardware Support, and Mandriva seemed to come up with a good few recommendations. So I burnt a live CD and gave it a spin. Detected the wireless card first time, asked for my WPA key, and that was that. So, I installed, and it's currently wirelessly streaming mp3s in the kitchen from the iTunes library up on the little NAS server at the top of the house.
Of course, the stray wifi rays will be giving the poor local orphans leukaemia. Never mind.