nimbey,
we did not have G/E's when I was at Fairford nor when I was on 48 in FEAF. When they were first introduced I do not know, but it would probably link up with the introduction of the Direct Entry Air Engineer. Previously you had to be at least a J/T in the airframe, engine, instrument or electrics trade.
Which is why as an Air Radar Fitter I could not be an Air Eng . So not being comissionable (at the time) I was selected for Air Signaller. However before I could start the course they suspended training whilst they 'reviewed the requirement'. Best thing that ever happened as far as I was concerned !