Plastic Rover heaters are the same mounting and controls as Moke heaters. They need two hooks on the lower firewall and the control panel screws into the underside of the dash.
Unlike Moke heaters, the Rover ones have the water hose fittings on the passenger side of the car so they are easier to fit.
Moke or Rover should fit into any mini that doesn't have the big switch panel like Laylands had. You just need the fire wall hooks which can be made out of sheet and rivited into place (better welded but hard on a car that's not in bits).
Hot air comes out the front of the unit or out of the vents that feed the demisters. It does not connect to the dash A/C vents.
In the photo, there is an air conditioning cover panel that surrounds the heater controls. The plastic below the controls is the heater.
I have a Rover plastic heater that I can sell from my 94 Mayfair (the one in the photo) but in Sydney you may find a local supplier is better because postage would be expensive.
M