A thorough Google only turned up lots of reports of this problem, but no solutions. After a bit of experimentation I managed to get things working - for anyone else having similar problems, here's the solution:
Download the windows XP drivers from Canon
Run the .exe which will extract them to a folder
Plug your camera in and let Windows fail to find a driver (takes a little time) - then select the Advanced option to find one and specify the folder where you extracted the XP drivers - make sure that the "Search Subfolders" is ticked.
Let Vista do it's thing and voila! your 10D is now working under vista - at least enough for the EOS Utility to download the shots - I haven't tried the remote shooting etc. just yet but will keep you posted.
Keep in mind that Canon don't actually support this and I'm not guaranteeing it in any way - but it worked for me

Hope this is of help to someone out there
Cheers
John