Insurance start dates - gap in cover

I am taking out a new car insurance policy for my 2 cars later this month, and have realised that 1 of the vehicles will be uninsured for 12 days in order to align them into a multilcar policy. The insurance company won't allow me to amend the cover date, and can only cancel the new policy and restart it for both vehicles on the earlier date (with a hefty admin fee). I don't need to use the vehicle during the 12 days, and it will be parked on my driveway. Can I leave it here for this period of time or do I need to SORN it?