PilotChris........during my Stages there was approx 20 at Stage Two, 6 at Stage Three and 3 at Stage Four.
I think these are fairly typical numbers. All in all, I believe CTC have approx 4000 applications for the Wings programme each year and at the end of it all have 12 people on 12 Courses i.e. they train 144 each year (this is just for the Wings Programme, I'm not too sure about their other ones).
Hope this helps