It might also be worth noting that BA codeshares with Cathay Pacific and Qantas on the HKG-BNE route. You could fly LHR-SIN-SYD / BNE-HKG-LHR with BNE-HKG on QF or CX (but BA flight number and all on a single BA-issued ticket). If you coupled this with SYD-NAN-BNE, this would cut a connection in Sydney. Just something you may wish to check.