We had a similar problem some years ago when a bloke across the road insisted on blocking our driveway with his car, and that of others. When challenged he said he needed to park it there so he could see it out of his window. Sounds a bit like your offender. Its not an old Merc by any chance is it as it might be the same person as he did move but I don't know to where!
One night he parked across it when our car was in the drive and I needed to collect my partner from New Cross station very late one night. I could not get the car out. I knocked on his door but he refused to answer it even though I know he heard it and knew what the problem was. Furious, I called the police for advice and they actually sent a car round. They eventually got him out of his house to move it and read him the riot act. They advised me and him that a crossover has the benefit of public highway protection and hence the bloke was effectively obstructing the public highway by blocking the drive. I think that might be the way forward for you? However if the person is likely to be agressive towards you then seek advice before approaching him or get the police to do it. It is apparently their job not the Councils.

You can reinforce the point by getting the Council to paint some white lines across your entrance; I think its about £80 for a single driveway.

Best of luck