I believe that by the mid-1960s BKS divided their types by North-east airport, certainly on the London runs, with Viscounts from Leeds, 748s from Teesside, and Britannias from Newcastle. The whole Teesside operation was rather abruptly given up around 1967 (there was a paper insert into their timetable saying so), and the 748s were then sold. The 748 was a good aircraft for coach-air holiday Its, as the 44/48 seats nicely matched a typical coach of the era, whereas 70-odd seats in a Viscount didn't.
Jersey/Guernsey were particularly weekday popular destinations for flight planners because their duration slotted in nicely to do a morning business return to Heathrow, then a mid-morning departure to the Channel Islands, and back in time for the later afternoon business demand again to Heathrow. If you didn't do them every day there would be Belfast or Dublin at similar times.