Soldato
Smear Nutella under their car and van door handles. Leave a Post-It with a warning "Next time it's poop"
So OP, you have had about 5 people tell you that phoning your local Police and getting it towed away is the best answer.
Its annoying me and I can only hear it through the open window. I feel very sorry for their immediate neighbours who have 3 children under the age of 5 that they will be trying to put to bed.
Can you not get all of the neighbours together and put a mass complaint in and see if you can get them moved on?