As an aside to my earlier post #74, those first flights in 1955 and 1958 originated at the Air Terminal on the South Bank, site of the Festival of Britain 1951. The later Geneva flights we joined at the West London Air Terminal in Kensington (Earls Court).
It was great to check in, have a snack or a drink, no coffee culture in those days, and then take the appropriately named bus to Heathrow.
As I recollect it was free, I say again FREE, tell that to the Heathrow Express.