Well just tried it again without it and still no spark. This capacitor was the only thing that ended up being different last time after trying several other coils, coil leads etc etc.
About the only other thing I can remember doing that might have effected it was unbolting, removing then re-installing the computer. Perhaps while adjusting the timing I have caused the ECU to stop working and taking it out has reset it???
Any and all ideas welcome here.