I'm no expert but I would suggest your neighbour doesn't have any right to park anywhere in a particular stretch of roadway. The roadside in front of his house doesn't belong to him, it's part of the public highway. The 50cm of your dropped kerb is not on your neighbours property, it belongs to the local authority. His property starts at the garden gate.
Assuming there are no parking restrictions in the road you could park in front of your neighbours house should you wish to, and he could park in front of yours. It may cause trouble but that's it.
If he is making it difficult for you to get off your drive on purpose he is being bloody minded. If you consider is he causing an obstruction you can ask the police to look into it.