HeathrowAirport
Not a guess, an answer: Neither. Following the accident BA suddenly found itself a 777 short, so there was a change in Fleet utilisation and a 747 was slotted in.
BA continues to operate 777's on Shangai-London, an equally 'cold route' using Chinese fuel. It's also going to be using the 777 on one of it's HKG services this Summer ( which often routes home via overhead Beijing and then onwards via Siberia), and there is the possibility of BA using 777s on NRT this Winter......not exactly the warmest of routes either.