take note of their reg numbers, and when they leave send pictures etc to the council. I'm sure there is an up to ?20000 fine for "fly tipping" etc(?)
if only you could fed-ex the litter back to their houses.
they are probably doing it cos they have converted their own homes and streets into slums. they want treated like adults, they demand respect, they demand rights, they don't deserve anything, and should not have respect or rights until they have earned it.