Leave a note on the car asking them to not park their sale cars in spaces used by residents of the road.

This may be ignored, so prickstick a large sign saying the same on the screen, after a few times they will get hacked off and stop no doubt,

No damage to the car, just an inconvienince like the one he is causing.

Teh council should be sorting this for you, but don't hold your breathe.

I personally WOULD be annoyed if a non resident was taking up spaces in the street, parking is bad enough, just good manners not to take the piss.