I had this problem a few years back when a woman over the road insisted on parking up my garage, I couldn't even open the door. She would say "Oh I was just dropping my shopping off and forgot to move it when I'd done."
So, I left it the next time.. Then banged her door at 5:30 in the morning when I had to go to work and couldn't get my car out of the garage. She wasn't happy and started gobbing off about how I'd woke her kids up.. I told her that I could always call the clampers if she'd prefer that, including the cost of my 25 mile taxi ride to work.
It never happened again.