So I found a BA flight LHR - HKG and a QF flight HKG - BNE.
I can book both individually on BA.com, but the HKG flight is priced at 80,000 miles (one-way).
It doesn't seem possible to link them in one booking on BA.com, so I guess I need to call to get them combined in one booking for 100,000 miles. Will it be straightforward for the agent to do this?