Pan Am operated a lot of charter flights with wide bodied jets. I saw four at Gatwick one Saturday in the early 80s although I think that one was scheduled (IAH route). Also Transamerica (747), American Transair (L15) and probably other US supplementals. I even saw a United 747 in the 80s on a charter from ORD at LGW.
I think that Nationair had a 747.