I did it in a Viscount too; BEA from Inverness to Sumburgh. I was invited to the flight deck but there was no jump seat fitted!
Had the same experience on a Cambrian VC7, LPL-BFS-LPL night newspaper flight in 1970. Them were the days lad! Wouldn't happen now though.
As for an entire plane load of pax standing up, naaah!