Ok, so this weekend I managed to chop out the underconsole and find a way to mount the heater controls. To make them fit here, I had to chop out the aircon switch (this car doesn't have aircon, but if yours does, you can fit it underneath the other switches next to the screen.
Once that was done, the two halves were filed flat so that they butted together, and then a very thin line of aluminium was used under the top lip to give it some structural rigidity. A top plate with folded "ears" was added, and this bolts up to the original holes that held the front console plate.
Once this is made, the back foam part of the console has to be cut out to accept the cable mechanism. It will fit, but it's a f**kng pain getting it back there. TIP: Connect the blower motor wires to the fascia, THEN struggle to fit the cable mech. The result looks like this:
Full cable travel has been retained, but unfortunately you can just see the front lip of the aluminium plate. I can live with that for now.
Also note the bottom lip and the two top "ears" in the main section; these are where the aluminium frame for the screen bolts up. There are captive nuts behind the holes.
Next to put in is the screen cage:
This is just for demonstration purposes; you have to screw the screen in first, then offer it to the hole, so that it looks like this. Make a point of feeding the switch plugs through their holes before bolted together!