Well, botched the LHD/RHD part and I too am a bit confused. The base car is a Hillman Minx Series IIIC for sure and they were assembled in NZ as the Humber 80 and a later variant, the Series V in Australia as a Gazelle but still using the Hillman name.
But, as you say, neither country would have had a LHD variant.
I have now visited over 25 sites dealing with the history of the Hillman Minx and have come up with nothing but the above two and the Iranian and Japanese versions.
Good luck!!!
Bill