I visited as a BCal customer for a bi-annual 1-11 sim check just once in about 1974. I seem to recall two 1-11 sims. The BEA 'Super' 1-11 version was equipped with Decca Omnitrac 2nd generation moving map display. ( I half expected to discover it had triple INS, Loran A, and a Polar Path sextant as a back up, since the taxpayer was covering ). I also remember as customers that we were allowed to use a rather smooth middle management type restaurant for lunch. I came away with the impression that it was all rather civilised, and remained somewhat envious of gentlemanly Corporation standards.
A while before that, I shared a flat in central London with someone who I once accompanied to an audition as a potential presenter of 'Blue Peter' at the BBC near Shepherd's Bush. ( me just being nosey, and I never asked for a badge ) What struck us was that the offices and general atmosphere at the BBC was identical to that when visiting BEA.....even the door notices seemed similar in look. My pal never took up the Blue Peter option, but he had flying background as well and joined BEA as a second officer on the Vanguard instead. Salary was about the same........