I didn't work for BOAC/BEA but if I remember correctly the Argonaut and Comet used for Apprentice training were parked near the Harlington Corner-Hatton Cross road through the hangar area which you could access by public bus!
G-ALHJ by
David Whitworth, on Flickr
BOAC 1971 Apprentices2 by
topemup, on Flickr
the Argonaut ended up on fire-training by Perry Oaks Sludge Works...now T5?....what of the Comet?
Air-Britain : G-ALHJ