Hi Bob
Jefford's book 'Observers and Navigators and other non-pilot aircrew etc' has a bit on the subject.
From 1945 onwards Transport Command had been trying to persuade the Air Ministry to award aircrew status to air quartermasters, but it was not until May 1962 that the QM badge (in 1970 changed to LM badge) was awarded. Incidentally it was the first RAF flying badge awarded to the fairer sex, as there were 10 women QMs in 1962.
Do you remember that on our Herc course, the newer Flt Engs and AQMs did not get their flying badge until successfully completing the OCU? There was then a small parade and 'tea and stickies' were served in our crewroom.
The book does not appear to give the date the despatchers (as they were then known) were first used, but I think they were in place by D-Day and maybe earlier in the Burma campaign.
Cheers Brian W