Phil, I have a similar problem but no visible leaks. The car has been standing for some four months due to lockdown / shielding and being some 4 miles away. I did sneak there the other day and the car would'nt start, the starter just clicking as if the battery was flat. I fitted the charger and it showed 14.7 volts.
Checking the oil it was way under minimum so I presume wet sumping. I shall try a battery pack in the next few days and see if a boost helps, otherwise drain the oil and refill the tank.
