I am classing this as a fix...

After allot of testing, scoping, driving, measuring & fiddling, I have replaced crank sensor and it has been fine since

I was fiddling around and moved the crank sensor multiplug and engine tone changed. Scoped crank sensor and when pressing the connector plug of the sensor while engine was at idle i got this capture.

Removed the multi plug and it had signs of corrosion

Darren