hire a hoodrat to loiter outside you're shop. "watch your car for 40 quid" either that or just pop into restaurant, "who's ferrari did i just drive into? i'm really sorry but i dont have insurance"
if you're an architectural ironmongers, wouldn't it be awful if a customer dropped a 25kg box of nails and spilt them all over your drive.
facebooking pictures of the owners and car parked on your drive might deter them, especially if you start a group "prattish parking" or something.
