Welcome aboard Simon
Super/Champ Sprint were big my big faves BITD too.
Not many of them around nowadays unfortunately.......I was lucky enough to pick up a Super Sprint about 10 years ago and I'm not letting it go!
I think I've only seen 2 others for sale in the UK since I picked mine up and one of those was very much a project.
Champ Sprint might be slightly easier to get hold of, but there still aren't many around. It's an Atari System 2 game btw and uses the same hardware/cabinet as Paperboy if that's of any help in searching one out. Mind you Paperboy is pretty much as hard to get hold of these days too.