Hi Mate @dr_broon. It's bad news I'm afraid I got a couple of the switches in and dismantled them to see if it's possible to fit the parts from the heated rear window/hazard switches into the buttons of the lower down A/C and Air Recycle buttons. I've took some pics of the exploded switches and how I tried to swap the bits over.
The switches dismantled: We'll call the heated rear window switch "Button1" and the Air recycle one "Button2"
Although the circuit boards are almost the same size, the actual switches on them are completely different. The Button1 is a bulkier one (see pic below), but with less pins.
I thought I might still be able to fit it inside the casing of button1 inside button2 though so went ahead and tried it. There were bits of plastic that needed removed from inside the button2.
Time to get the tools out!
After cutting out the innards
Unfortunately, when I tried to fit the board from button1, there was no way it was going to work. The rear of the button1 where the plug goes was too bulky compared to what had been there previously. The Switch inside was also too bulky, and the bulbs were in totally different places. Button2 has two casings, and one slides inside the other. The board from the button1 was fouling the casings so they couldn't move freely. I even tried cutting the rear underside half of the casing away, to see if this would allow movement but no luck.
Examining the boards, I noticed that the button1 has a larger switch with less pins (only 5 on the plug socket on the rear of button). Button2 has a smaller switch with 6 pins, and has 6 pins on the plug socket on rear of button. Looking at the printed circuits, both are wired differently. I'm thinking though, if you can check the wiring diagrams for our cars, and work out what wires are what (3 or 4 of the wires on button2 are for the bulbs, but go through the actual switch where as on button1 they wires for the bulbs don't go through the switch.) you might be able to rewire button2 to use as heated rear window/hazard switches. Would be a case if identifying the wires, cutting off the plugs from the heated window switch and the new button2 and getting another plug from old tubs wiring for the air recycle switch and A/C and see if you can rewire the plugs to work? Think it might be doable, although I'm no expert!
But as for swapping insides around, it's a no-go I'm afraid mate. If you need any buttons, I have tons of them from our old Civic5 parts dept that we used to have. Just gimme a shout.
Dave