Just to add to this thread, Jeremy Vine show on Radio 2 (yes i am an old boy) was talking about this issue on Monday. It is happening more and more town centers seem to suffer a lot due to lack of parking and high prices but it is happening all over. People just dont care.
One person told the story they live next to a school and people just parked on there drive whilst they went into school for parents evening. Owner blocked them in and charged the 50-00 to get out.
A number of people have been taken to court, some have been done (for protecting own property) others got away with it and the person who parked had to pay up.
However the law says its a civil matter and you have to pay to take them to court to ask them nicely to move there car unless its a danger (eg petrol or gas bottles in the back of the car) or its been stolen - all of which is what has been talked about here.
However if you take the law into your own hands then the person who parked on your drive can (and do) take you to court and it can cost you.....
However ending on a light note a
garage owner got fed up with people parking in his lot so put up some private parking signs saying if you park illegally he will take action and charge you for it. His action is to raise the car and leave it on Axle Stands and wont let it go till they pay up. He did say he had been taken to court 3 times but he had won each time...