Hi Paul, glad to hear you didn't get earthquaked !
@Mittzy and some of his mates, figured out its the starter relay under the right hand side cover. The spade connections get dodgy and don't send enough power to the solenoid to drive to pinion gear into the flywheel (I think that's why rocking helps). I had that problem for several years. Rebuilt starter switch, big battery cables, all the usual suspects. After I read what they found, I disengaged the terminals from the relay socket and cleaned and re-crimped them. I then cleaned the blades on the relay, then slathered them with die-electric grease and plugged back in. Hasn't done it since !