Flash, you are right. I don't recall having a choice. At stage one interview you were asked who you preferred and why. BOAC and BEA had equal pick of graduates depending on the airline's staffing requirement. The selection procedure was split into three separate visits to the College. Pitching up for part one the night before, at dinner (provided) in the cadets mess, one current cadet joined the table of candidates and during conversation said that he had been "earmarked" for BOAC VC10. No idea if it was true or how the earmarking took place.
I informed my interviewer that I preferred BOAC and when asked why, I further replied that it was the only job where you got free transport from pub to pub. I fell of my chair larfing but on regaining composure, I noticed he looked decidedly unimpressed.