There were 436's still with us in late '76 - but maybe only 'PFJ - I did my command base training on it - in fact it was still pounding the circuits in Jan77 when I last flew it doing crosswind landings, after which it was all 336B/C's.
G-ALHI - love your user name - it was the aircraft in which I last flew with my father when he was checking out on the Argonaut for Air Links - circuits at LGW - great fun