In Lancashire they have the "Speed enforcement Team" which drive police vans but have orange lights on instead of blue. They were advertising for it in the paper about 6 months ago. They have no power of arrest as far as I am aware, so they can't pull you over, which is fantastic if you have a jammer, because the only dodgy thing about them was if the police pulled you over and inspected your car.

Oh, and they work shift patterns too, including bloody 11pm at night at the bottom of hills