pulse1, (your #6238)
AFAIK, the RAF trainees from both Canada and the US all returned to the UK after getting their wings overseas. The decision about their operational future was made at home; after a month's "UK familiarisation" Course they would be sent on to the appropriate Operational Training Unit, and from there to their operational Squadrons. I am certain about the US, but there are ex-RCAF among us who could confirm Canada.
In both places, there would be a small proportion (in the "Arnold" Schools 7% of intake) of the newly winged, "creamed off", trained out there as Instructors, and employed as such (for how long I know not) before return to the UK. In the US case they were intended for the BFTS - you can hardly expect them to be let loose on American Cadets ! (but one surfaced on my "Advanced" Arnold Course at Craig Field, Selma).
In the immediate aftermath of the Bomb, my tiny unit was being used as a parking place for latecomers who'd arrived in India after it was All Over. Among them was one chap who'd spent his entire war in Canada, logging 2,000 hours instructing on Tiger Moths (talk about a "One-trick Pony" !)
Danny.