Spotting holiday at LHR/LGW in July Aug 78. So far can only find CAM and my log of a/c "made" not the raw log, though I know it's still extant. Never wrote up the last few days as employment demanded more of my time!
Air Ceylon had a B720-023B 4R ACS leased from Templecord Aviation. I'm pretty sure I saw Arainna 727 at some point. I'd guess the service ended after the Soviet invasion c1980.
Luxair ran a Sunday service in 76/77. I made a few in those years when my only access to LHR was Wallace Arnold\'s coach tours from Leeds. CAM 78 lists LV LZD and another tba as Aerolineas Argentinas 747 287B\'s, can\'t confirm these unless I can find my raw log.