Just to follow up:
There are currently 4 J class seats (per BA) on CX HKG/BNE on 19 Nov 2019 (330 days out). This suggests that you might have more luck getting CX into Australia than NZ. You can then buy a Trans Tasman ticket or get an award redemption somewhere else.
Last edited by minz56; Dec 23, 2018 at 5:06 pm