Ivo
To summarise your results so far, you get a spark to earth, using the HT lead connected to the coil, when you try to start the engine. However it is just one spark and then there is no further spark.
I believe you have confirmed that you have a constant supply to the coil while cranking, (actually 10 volts during cranking ?). The ignition is effectively a standalone circuit, the section you are testing comprises
The pickup in the distributor
The ignition amplifier
The coil
Cable from pickup to amplifier
Cable from amplifier to coil
Just to give you an idea of the cost of these items, using
https://rimmerbros.com/Item--i-GRID010021choice of
Pick-up and Baseplate - Distributor - STC2898P1 - OEM £91.20
or
Pick-up and Baseplate - Distributor - STC2898P - Aftermarket £42.60
Amplifier Module - 35DLM8 - STC1184P - Aftermarket £18
Ignition Coil - Replacement for Bosch Type - Valeo - PRC6574P £19.50 (note there are coils from other manufacturers listed on the web site)
There was a change of connector around, or after, 1995 so you will need to confirm which type of connector you have on your distributor. My 95 Plus 8 has the STC2898 type pickup and baseplate. The later type is.
Amplifier Module - 35DLM8 - STC1184P - Aftermarket £18
or option of
Ignition Module and Link Lead - Britpart STC1184K £30.30
It is inferred that items marked OEM type are better quality, I purchased the STC2898P1 which is the OEM type, but I did have to take a file to the plastic connector to make it fit correctly into the slot in the body of the distributor
You can buy the parts from many different suppliers. I have also used britishparts.co.uk