Re SAA , the Monday non stop was 747-100 or 200 if they had the latter. interesting that it stopped in Uppington I thought it came back via Ilho do Sal , as you say they could not overfly many African states in those days As for BOAC stopping in Rome I am sure you are right now I think about it, BOAC had quite few stops there en route further east or south .
The Monday SAA non stop was quite a sight from the departure end of 28L , one I remember rotating at the junction with old 23R and being able to hear the real thunder of all those jumbo wheels ahead of the engine noise , Certainly the longest take off runs I ever saw at LHR