Parking in front of an entrance or exit is not permitted. This is not always clear. If the exit is clearly marked and a vehicle is parked there nonetheless, you can contact the police on 0900 – 88 44.
Make your exit clearly visible
You can put up a sign on your plot with (for example) the words ‘Keep the exit clear’.
Painting a cross on the road isn’t exactly a pretty sight. That’s why we don’t usually get involved in that sort of thing.