76 MK1 no spark

Hi, I have a starting issue on my 76 MK1, it died while driving and now won't start.
It was originally a 1.6 carb, but now has 1.8 8v carb engine from a 80 Passat)Santana that looks to have been done many years ago. It has this weird Bosch electronic ignition set up,


I don't fully understand it, there is a ignition 12v source connected to the ignition ballast, but as soon as you connect it to the ignition ballast it goes down to about 7v and 5v on the + side of the and around 2v on - side of coil. Looking at limited information online I think thats ignition ballast doing its job??? I have managed to source another ballast and it does the same thing.
The only thing I can't seem to locate it a signal from the starter/key for a full 12v to start the car? The ignition ballast has the lower voltage apparently to stop the ignition coil burning out when running.
So cranking the car and spark plug tester or old fashioned way of testing a spark plug on top of the engine I have no spark. I have replaced the silver Bosch ignition box in the pics again no difference. The load relay, spark plugs etc and still no joy. All fuses etc seem fine.
Can anyone point me the right direction? Or a local to me Wakefield/Leeds area mobile mechanic to have a look? Or is there a new better electronic ignition system) distributor I can swap to?

Sorry picture are not uploading. I'll keep trying