I don't believe it would be considered illegal even if your Humax does have a british accent. If you're at all worried, try it for a few minutes each night at first, and see if the NZ Humax detector authority becomes alerted.
New Zealand, though using the DVB-T standard are broadcasting in MPEG4 on DTT (marketed as Freeview|HD). So the answer to your question is no (assuming you are referring to a PVR-9200).
