As I recall a P2 could be issued by the Gliding School concerned which was useful as there was a lot of Cadet AE flying by the 70's. At Kenley (615) which was not a huge site our 'safety conscious' CO would not issue a P2 for AEF work until one had 100 P1 flights under the belt. A quick way to boost one's flights was to 'help' at a centre for a week or two when you were given a machine to use after the course cadets had done their solo's.
If my memory is correct I do not recall 'any' real classroom briefings for ATC flying at the time, Cadets were briefed in the cockpit and got on with it.