Tinkering tonight, putting things back which have been removed for fixing other things.
For some reason the perpetrator of the wiring mess ground away the inside of the switch blank hole
I can't figure out why, since there was a standard foglight switch in there! With it like this, a stock blank just falls out of the panel.
Meh. We have spares!
Remove the screws and the plastic switch holder comes away from the wooden trim
Pop the switches out to transfer to the new holder. The switches at the sides will come out with the panel assembled, but the hazard switch only comes off with the plastic holder removed.
Reassembled with a blank and ready to go back in
I also got the TPMS working again. Said perpetrator had wired it to the wrong side of the hazard switch so with the switch removed for tinkering the TPMS had no power. I had tidied up the wires and just put them back where they came from, assuming (foolishly!) that the perpetrator had got it right. Alas no
The TPMS was drawing power through the electronics in the hazard switch, so while it worked with the switch plugged in, it stopped working as soon as you turned the switch on!
Wired up properly, it fired straight up with the ignition. It powered up with a red light then flashed red/green for a while as it detected all the wheel sensors (presumably since the battery has been off for a while), then showed me a green light to say all was well. I tested it by letting a tyre down, since neither Vera nor I knew what it would do in response to a flat! It flashes orange at ~1.5 bar, and goes solid red at ~1 bar. If all is well it turns the green light off after a few minutes unless it detects a fault.