Someone recommended me this program to try out

http://www.simplifymedia.com/

basically lets your itunes (or winamp) interact any other ituneses you want it to on the net and stream (but not copy/download) stuff from their library as if they were connected on a local network.  Seems like a good enough idea, and works away in the background I think.  If anyone fancies trying it out, my username is orgoglio (I'm sort of impatient as I've no-one online at the moment who wants to try it out).