OK, but I'm not entirely sure you're right.
Heron was the name of the car and MJ1 was the model (Heron also made other models).
The Heron (Lotus-Esprit sort-of copy) was designed and built by Ross Baker of Rotorua. 22 or 24 cars were made, depending on where you read about it, and Baker needed help financing the project so Summit Engineering became involved. They eventually folded I believe, which is when Baker bought back the two-thirds ownership of his company that he had sold them then continued to make his other models (MJ-1 2+2 and various others).
There is actually still a Heron Cars Ltd. website.