In the late '60s (1968-) Autair operated Leuchars-Carlisle-Blackpool-Luton with HP Heralds. Route may have varied Carlisle/Blackpool morning/evening or day to day but I can't remember. I don't know how long they lasted, I think not long, but they were still going when I left Leuchars in '69. At Leuchars they had a small pan and building up near the SAR helicopter flight.
BTW I did a flying scholarship at Carlisle in the early '60s, seems like an age ago!
ExMPA