Thanks for the comments and the welcome to Eurobricks.
Unfortunately the car does not have suspension, as I wanted to keep it simple and I couldn't see a way of fitting it in at this size anyway. I hope to progress to suspension, gearbox, etc in future MOCs. It is driven by one L motor sitting behind (in parallel to the rear axle) - this proved a bit of a headache to fit securely, as it kept trying to twist away from the differential gear when powered. It is a bit slow, but I suppose that is to be expected.
I will try to find time to post a shot of the underside when I get time.