So Ed, this thread did get a bit lost. I'll try and help a little. Dont know about the current models but my 2012 plus 4 (without aircon) has the aircon button on the dash (top right button) but it does not light up with the background lighting, so is kind of secret. However, it does light up when I press it. The electronics are there behind the dash on the circuit board.
Under the bonnet, the heater box has space for the cooling matrix, with stubs of pipes running in and out of the sides of it. Thus it would cool air going into the box under the dash. Of course none of the compressor, radiator or pipework is there. I did wonder about a retro fit but it was a bridge too far
