Seem to have an intermittent issue with starting and its really bugging me now

A good number of months ago my car died on a run under power. Pulled over jumped out had a visual check nothing out of the ordinary. Jumped back in and "click" no starter, AA out recovered home. Click fix of new relay and starter jumped back to life but engine was playing ball, no spark. Attempted to start the car on a off over a period of a few months (it was in hibernation for winter) nothing, AA out, much head scratching just the offer of a tow to a garage, not much help on a sunday.
A little while passes, thumbed the started when passing her in the garage and she burst into life

. Ran her about for a few weeks, got her serviced then a week or so later, nothing again.

Where would people suggest looking? Guessing it might be a dodgy earth? Coil?
Any help greatly appreciated
Anddrew
R500(k)