I'm certainly up for testing a patch.

I was actually hoping to try and fit an old HD to my main PC this bank holiday weekend (where does the time go?). That way I could try installing XP and see if the game works with the same hardware (just not W7/drivers). By the sounds of it you've identified the issue though; probably no point me trying that now?
If you'd need extra confirmation that it's a W7/nVidia drivers issue I'll still give it a go!
[Update] It would seem to be something to do with the nVidia drivers. I installed the latest W7(64bit) version today (197.45) and found that I now get at least a few frames of animation after starting the battle (before the same issue occurs). Hopefully I'll be able to give the HD/XP a trial tomorrow.