If it helps, his Service Number was 90037. The London Gazette has the following….

LG Issue 34304 14/7/36 page 23.
RAF Special Reserve, General Duties Branch.
John Randle Garrett is granted a commission as Pilot Off icer on probation. 12/6/1936.

LG Issue 34428 20/8/37 page 6.
Special Reserve, General Duties Branch.
The undermentioned relinquish their commissions on 1st July 1937 consequent to the conversion of No 502 (Ulster) (Bomber) Squadron from Special Reserve to an Auxiliary Air Force Squadron.
P/O Garrett is one of the undermentioned Officers.

LG Issue 34495 22/3/1938 page 8.
Auxiliary Air Force, General Duties Branch. No. 502 (Ulster) (Bomber) Squadron.
Pilot Officer John Randle Garrett is promoted to the rank of Flying Officer. 1st February 1938.

LG Issue 35158 9/5/41.
Auxiliary Air Force.
Flying Officer John Randle Garrett (90037) is promoted to the war substantive rank of Flight Lieutenant. 3rd September 1940.

I can’t find anything else in the London Gazette but I would have thought there might have been mention of his leaving the service?

There is also a very brief mention of him in Flight Magazine stating that he was wounded. I think the issue was 18th April 1940. There were no further details.

Regards,

kev35