I was also after this info and posted in the Clubsport thread before seeing this page!
I remember reading the press release when they were launched and it did seem a bit vague on numbers. They seemed to imply there would be 'around' 1000 units produced but with no hard stop number in place.
I think they were just trying to get as many orders in saying it would be 'first come, first served'
However being £31-32K basic price + options - it was probably a tough choice for a new car with some many other competitors (which are all faster! - Focus RS, M135i, Golf R, S3).
Not sure how often this is updated but howmanyleft seem to indicate 514 registered Edition 40 cars at the moment.