quickest way to get rid of a harrassing officer is to stop him for a moment, get a piece of paper, write down his numbers then ask him for his name. By this point he will be getting a bit worried. dont antagonise him but make it clear that you are recording every time he makes a point of talking to you for no good reason.
He will start to worry about an offical complaint and soon leave you alone.
The police round dartford are just the same, i am always polite, get out of the car b4 they do and greet them at their window with my drivers licence in hand and a smile.
Take their power away from them in a confrontational situation and they will be on the back foot.
good luck