For anyone who may run into the same problem...

Patient was a 1988 A100 (2.0 RT engine) which broke down. Extremely
difficult to start. If I can start it, then it will run for about 10-15
mins then cut out. Not driveable as stalls too easily. I'm using regular
unleaded for which I believe the timing should be 8° BTDC. Bizarrely I
found that advancing timing to around 30° it would start quite easily....

It took me about 6 months but I finally found the problem. It was the
coil. I had actually tested this very early on but moved on because the
resistances were in spec, and I was getting a spark anyway.
It also fixed an odd misfire I had beforehand below 2000rpm under load.

I'm not sure I understand the theory. I guess I had a 'weak' spark which
needed more advance to burn the fuel in time.

I'd never have found it without a car to swap bits with (or lots of
cash). So it's worth noting that the fuel distributor, ISV, coil, warm-up
valve & distributor from a A100 with the 2.2 KU all seem to work fine!

Gary