CossieMoon, I have found the ECU type thing. Well, I did on my wrecked car anyway. I've taken out both the ECU's that are wired to the Warning Lights/Fault display and have them put aside incase they are, or will be, of any use. I'll check the horns too, thanks!

Marty, that "prong" switch is what I assumed triggered the DoorOpen warning. Thanks for the info on where the real switch is. I will check all doors, as none seem to give a definitive or constant reaction on the fault display...more of a random or multiple door warning.

I've just noticed that the left rear warning light now comes on whenever I engage reverse.



I will keep posting updates as I check/solve things. Hopefully this will help someone else out in the future too.