Just a quick update...
I have been so busy on stuff I haven't had time to continue my thread here.
In short I have more or less diagnosed the refusal to re-start when hot to it being caused by a hot coil.
If I take only a short run which makes the engine work hard for say 4 or 5 miles then stop the engine it won't re-start until things cool down, say 20 to 30 minutes. If I switch out the coil to another one sat alongside the first one, at the same ambient temperature, the engine re-starts instantly.
These are 12 Volt coils, running at 12 Volts. I have 3 or 4 coils one a new Bosch, all of which perform perfectly well when the engine is running but all refuse to re-start the engine immediately it's stopped if the engine has been working hard, unless you bump the car off down hill or with a tow.
I have moved the coil from the bulkhead to in front of the radiator. Am concerned about protecting it from water (rain and splashes from puddles and standing water) but for now it seems to have fixed the problem.
The car is laid up for now, I need to get some longer/stronger springs, it's WAY too low, grounding out on the slightest bump, speed bumps can stop me because I have less than 3" clearance, crazy!
Will do a better update asap.