See what the Beat Bobby comes back with - don't hold your breath.
Next time you do the job do it so it's completed just as the manager arrives. Tell her the suspected prob. and reassure her that if anything happens like muck on glass then for her to call you and that you will sort it immediately.
Be prepared to go back and clear up any mess matey boy leaves and if you know it is him report him again. Other than that ignore him completely and watch your back. But find out where he lives. Report every incident and make a nuisance of yourself to the police.
Then ...
If that doesn't do it then get a few of us to go round his gaff on our motorbikes and sit outside looking at him and his motor and revving our engines a bit in an intimidating sort of way!

If that doesn't work then send Toshimoto round to do some Feng Shui on his living room!

Maybe send Squealy Queen round to hit him with his handbag! Or one of the JW's can attempt to start a Bible Study with him pointing out the error of his ways ...
(Those last 3 paras are a joke BTW)