Thanks for all of the suggestions. By formatting my search differently, I'm already seeing different options! And I see that CX flies direct from HKG to MAN, which would also work as a destination for me.

I'm looking at PNH-KHG in econ, and HKG-MAN in biz. Should I book it as one ticket? If so, can I upgrade the PNH-HKG if biz seats become available?