Genuinely, I'm not sure I'd bother. They have better things to do than studying CCTV looking for a driver who has scuffed another's bumper, maybe without realising, and given the cuts to the police they probably don't have the manpower even if they had the inclination.
Not saying that I like the situation, but that's the reality. You could try bugging them every day to ask them how they're getting on, and they may do something just to get rid of you, but a full on complaint? Not worth it, as it won't be against a specific officer so will be ignored.