As regards LBA to the Channel Isles and (variously) BA/Northeast, Dan Air, Air UK etc one needs to differentiate between schedules and IT charters.
I remember in summer 1975 there being multiple BA/NE services on Saturday/Sunday only some of which were schedules. Others were for tor companies - Wallace Arnold rings a bell.
Later Dan Air operated Viscounts to jersey, mainly I think for Hards. Probably 748 operations to Guernsey were similar.
We forget how big the Channel Isles were as a holiday destination until foreign IT services got to be just as cheap.