Ok Update.
It was the Bulkhead Connector!!!
I had checked it, wiggled it etc 3 or 4 times
but failed to notice it had come out slightly on the lower left corner. Pushed that in nice N tight and she fired right up!
Has started now 5 times in a row on different days so pretty sure that was it.
Thank you all for the great explanations!
Just a suggestion, GET RID OF IT (the bulkhead connector)! If it arcs and shorts out, with the accompanying wiring fire, what have you saved? And trust me, it will arc and short and it will catch fire.
