Yeah SQ is a valid one stop only option.

I might suggest the following on Star Alliance carriers LHR-YVR on AC then YVR-AKL-CHC on NZ. Saves any US immigration hassles.

Theres also the option of LHR-HKG-AKL-CHC on all NZ flights.

If you do either of these Air NZ options I highly recommend you book the AKL-CHC leg on NZ303. Doing so means you clear customs in CHC which is much smoother all round than having to do so in AKL.

This flight operates at a time that meets the arrival of Air NZs HKG and YVR services. You simply change planes airside, luggage is transferred automatically.

Hope that helps.