Hi Kiwi Norway,

I rang Air NZ a while ago about a similar situation, as I found booking 2 separate flights (AKL-LAX on .co.nz and LAX-LHR on .com) made my trip much cheaper. Anyway the lady I spoke to assured me that there would be no issue with this but advised me to link the 2 bookings to ensure it went smoothly at the airport.

Unfortunately I didn't end up booking the fights so have no practical experience, but she was very confident it wouldn't be a problem.

Hope this helps.

Cheers