Originally Posted by
Bullswood
Re Scillyisles advice of a stopover. If you do consider this, I'd suggest that for the outbound, you look at the BA +CX routings via HKG also offered by BA (which are strangely sometimes cheaper than the BA through service). It's slightly less mileage anyway and thanks to the more even split of sector lengths and different service standards, you'll get a much better night's sleep into Sydney.
If breaking in Hong Kong, it is possible to take a daytime service from Hong Kong to Sydney and no issue at all getting to Australia time
My advice , if going straight through without a stopover, would have been to take a different route where can leave UK in morning/lunchtime and arrive into Sydney in the evening - much less tiring and easier to get into AU time