Technically, yeah, and short of paying for a tow truck to remove you and place your car safely on the road immediately off my driveway and invoicing you for costs, there aint much I'd legally be able to do about it.
If you overstay your welcome in a private car park, the only thing they are legally able to do is bill you for lost revenue, and by 'lost' revenue, I don't mean what you should have paid but didn't, I mean revenue that they lost as a result of a paying customer not being able to use your parking space! Bear in mind that 99.99% of the time there will always be another spare space.
Another thing to point out is that in contract law (which is essentially what you enter into by using the facilities of a private company) you cannot impose financial penalties on anyone for a breach of contract.
To summarise...
The invoice that the guy received from the private parking company in charge of managing the service station's car park was not worth the paper it was written on!