On to a cars window screen asking them not to park across my drive again?
I've already done it 
Bit of more info, I live next to a little shop and outside the shop and my house is a small car park, enough for four cars , it is the only way I can get into my drive, there has been a car parked almost right in front of my drive since before Christmas but I can just squeeze my car past it but other people keep parking right across my drive, now I don't mind so much if they're just nipping into the shop but when they do it and go into people's house (which have empty drives) it really boils my blood, so aibu?