So I brought the in laws an IGLOO STB and plugged in a DDS401 amplified indoor UHF antenna (powered) DVB-T compatible / freeview approved.
This type can be positioned vertically or horizontally.
Horizontal - I can get all the freebie 30day channels and media works channels, no tvnz.
Vertical - I can get all the freebie 30day channels and 4 free to air tvnz channels but no mediaworks.
I've bit the side knob cranked it the max and suspect this is the gain control.
Should I answer my own question and get a refund on the sixty pinger antenna from Noel lemming and get an outdoor installed for the few hundy.