AndyGPR

As Michael states, the cap you bought is indeed a Royal Army Education Corps item; "sexed-up" with a Glider Pilot Regt. cap badge to make it more desirable. I saw this myself and remembered the seller as being someone from whom I'd bought some original GPR buttons for a friend just a few weeks earlier; 'td999' I think is the guy's username?. It's not uncommon to see sellers listing both good and bad items and in their defence, I guess they can't possible know everything.

You mentioned that the "badge appeared to be correct". I'm as close as you'll get to an expert in the field of Glider Pilot Regt. insignia so if you could post a photo of the badge, I'd be happy to give you an honest opinion.