After some false starts and setbacks, I have a functioning Control Module prototype fitted in the car and it is working beautifully.
The basis for the unit is this Voltage sensing Relay Module I bought off AliExpress. Added to an interface with a Buffer OpAmp fitted.
I am leaving the home-made prototype board in the car for prolonged testing and should the results be as expected, I will have the above professional boards manufactured.
Check out the YouTube Channel for details.