Couple of suggestions to add.
First, in my experience going with EK from the UK 'feels' more like 2 flights not 3 if you take the Sydney routing (A380). The stopover in Syd is very user friendly, with a dedicated transit security area that's close the incoming gate, and an EK lounge literally next door to security. I have found this quite welcome for a quick shower and stretch of the legs before the last 2:30 to Akl.
Second, if pennies are to be saved in J then I recommend Finnair. If you try Finnair on a straight UK-NZ-UK return then it's expensive. But, if you try some multi-legs eg. UK-NZ outbound, then Aus-UK on the return, there are some amazing fares available at least some parts of which will involve BA metal. The non BA metal bits will be either CX or AY, both fine airlines. In fact personally I prefer AY to BA anyway. So for travellers such as PaxBoy who actively want to do a NZ out/Aus back routing, this is worth a look.