Going to add another update.
I plugged my car in last night and got a code:
U3004
This corresponds to a start stop unit that my car doesn’t come with. Googling the unit brought up this diagram/
I noticed that it goes through the heated mirror fuse. I opened the fuse cover inside the car and noticed that the dash cam was piggybacking off this particular circuit (proper Nextbase wiring kit). I removed the adapter and just connected the fuse directly.
Now my audio system is working again
However I still have an issue with the clutch pedal triggering the boot switch. When I press the clutch before I start the car, the boot latch opens. If I start the car and get out and close the boot, I can operate the clutch without triggering the boot switch to activate as long as the car is running. Then when I park up the boot switch activates again when the clutch is depressed.
There is a switch in the clutch that prevents the car starting unless it’s pressed isn’t there?
The only thing I can think of is that I installed a Mazda 6 boot switch (in the blank space below steering wheel on right hand side) a good while ago (wiring harness was already in car) and perhaps this is connected to the clutch issue ? However the switch has been installed and working for 1+ years