Don't get tied up on which type goes where as it can change on a season by season basis and indeed sometimes within season too. BA will send the type that most "fits" the route, based on many factors. To give an example the LAS service started with a 777 but has since moved to the 747. The only fairly fixed LH routes are those that operate from LGW but this can also change, the MRU used to be a LHR 747 service and is now a LGW 777 service.