Might need a bit of persistence but I agree with the DDublin, MandaC & truthseeker.
We were in a similar situation a few years ago but it was worse because we had a car and couldn't get into our own driveway - generally it was visitors to our neighbours that were the problem.
I just knocked on the door and politely asked them to move the car - which they did, slightly grudgingly. This happened about 5 or 6 times over the space of a few weeks and I gradually got less and less polite. The last time I knocked I just rolled my eyes and pointed to the car. The next time I just aimed my car lights at their front window and beeped the horn until they came out and moved the car.
It didn't happen again after that - they didn't speak to us either but with these particular loo-lahs, I preferred it that way TBH.