Well Ivanhoe because in my experience reporting this stuff is a major waste of time even if I'd got the plate number which I didn't on either occasion.
If you are really lucky you may even get accused of harassing the person causing the problem by complaining about them and told you would have to bring a private prosecution against them if you want anything done.
I don't know anything about the numbers Graham is posted these are just my experiences with the local antisocial behavior lot (accused of harassing the person causing the problem by complaining about them and told you would have to bring a private prosecution against them if you want anything done) and the police (A. don't turn up even when you report a guy in the act of trying to break into a car outside your house and B. tell you if you do run over an underage unhelmeted kid on a motorbike going at speed the wrong way up a one way street you will go to prison and no they aren't coming to look for him. That was a couple of years ago. Maybe they've changed)
If you've really been told that by the police, then wouldn't complaining to the right people still be better than posting on here?
I'm not trying to be antagonistic. It would be great to look on here one day and see you posting that your problem has been resolved. But I genuinely believe that doing something about it (other than posting on a forum) will give you a better chance of getting it sorted.