i tell them i have a private bore hole and scorce my own water that seems to shut em up or...........
or the water is scorced from cornwall or from up north ect where there is no ban or............
its not water but an alchol based cleaner therefore not subject to a ban........
or more temptingly its neat sulphric acid seeing how they react if any of it drops from above when they walk through a door after you have cleaned the windows above just a thought