BA 09 did have the BKK to SYD route but as of April have put their continuing passengers on the QF flight. In reverse, Qantas no longer continues up to LHR from BKK. Unfortunately, Qantas has also reduced their equipment to the A330, so no more 747 service. The QF A330 is definitely a substandard plane compared to the 747. QF 24 does not have F any longer, just Econ and Biz.

As for the BA 747, if you can upgrade to F, do it. If not, go for the exit row, window on upper deck, lots of leg room and extra storage along the wall.

Enjoy the trip.