Thanks again, everyone. There are three entries in the London Gazette which are confirmed as relating to his National Service:
Cadet Pilot 30/4/57;
Acting Pilot Officer regraded to Flying Officer, 30/4/58;
(RAF Reserve Officers) Pilot Officer to Flying Officer, 8/2/59 (seniority 8/11/58).
A photo of him with a RCAF Chipmunk (with bubble canopy) has confirmed that he did some or all of his flight training in Canada.