I am leaving this post in place as a matter of record. Happily, Mr Pearce did get in touch and has been extremely helpful. A later posting will record some of the insights from his very kind assistance.
My 2006 posting about Dad's wartime experiences attracted a comment - the only useful one so far. This was from Trevor Pearce, as follows:
"I have been doing some research about my father David Pearce and his time in the RAF during WW2. it appears that our fathers did their multi-engine flying course together in Canada in 1942. I have more information if you would like it
I would be very very grateful if anyone knows Trevor and can contact him, as I know every little about Dad's time in Canada.
One thing that I have discovered is the context for the training in Canada. This began after the fall of France in 1940, when it was deemed too dangerous to train aircrew in Britain, and so the British Commonwealth Air Training Plan began. The scheme was enlarged after May and June 1942, but it began to be run down after November 1943. Presumably Dad would be back in England by then, flying reconnaissance.
Trevor Pearce's information has been invaluable, because it puts a date on Dad's involvement. Mr Pearce, do contact me - I would be so grateful!