G-BDXG, The 747-200 were mainly used on the SEA, YVR, SFO, BOM, CAI and DEL, and to a lesser extent JFK, BOS, ORD, IAD, DTW, YMX, MIA, EWR and YYZ which had more of a 100 service, PHL-PIT was a sole 100 route, apart from an occasion replacement aircraft.
The 400's on the other hand operated out east NGO, NRT, SEL, KIX, PEK, HKG, SIN, BKK, KUL, CGK, MNL, TPE, PER, BNE, AKL, SYD, MEL, ADL. Some African routes and All south American routes GIG, GU, EZE, SCL, CCS, MEX and BOG. Only certain Nth American routes got the 400's. LAX was the only one route which all flights were 400's SFO and MIA ere split 400, 200(100 MIA). MCO and IAH all so got 400 flights out of LGW, In the late 90's. Of course it was NOT uncommon to see 400's in other destinations commonly operating as replacement aircraft. Information is around the 95-98 era.