Just got a call from Shannons in reply to my email yesterday.
Spoke to someone who was much more helpful, and explained to me the restricted driver condition in more detail. It's not quite as bad as I thought, but still a bit of a pain, and they still want to put it on both cars.
They were happy to increase the value of the leopard by the same amount as just car however, and said they would be happy to talk about increasing it further if they can inspect the car.
Much happier with the service this time round, they are going to send me an updated quote and we'll go from there.
Maybe I just spoke to the wrong person the other day...