Hi Ken,
I've just looked at the original videos I downloaded (I downloaded 6 total).
Five are 23FPS
One is 30FPS
I chopped the highlights out of each video and converted each to MPEG-4. Of those videos four are now 25FPS and 2 are 30FPS. What would explain these FPS changing? Is it Video Studio just realising I am in Australia and converting appropriately? I downloaded it from their website so maybe they just tracked the IP and assigned the appropriate TV system to my software?
Anyway, I then outputed my final video edit, which contained each of these highlight videos cut up and put to a music soundtrack. It's this final video where the highlights are not syncing up with the music. They sync up perfectly in Video Studio but not when outputed.

I've put months of work into the video edit as well, only for it to fall at the last hurdle. Is there absolutely no way I can get around it now? Even if I have to go back to stage 1 and re-cut the original videos? What if I take the music track out, output the video to MPEG-4, then just drop the standalone video track to the music?
Thanks for all your help.