I think that if I found something suspicious I would call the police on their non emergency number unless I thought that it might be a bomb. I have to say in my opinion the police are doing themselves absolutely no favours here, I would be very worried if I called the police for anything these days. You immediately become a suspect and, in some cases, can spend lots and lots of harrowing hours, to all intents and purposes, in police custody being questioned. I am not saying that from any personal experience I hasten to add but this is my gut feeling. So, from my point of view, I would have to be very very sure that what I was reporting was beyond my suspicion and that I was very very prepared for the, possible, grilling that I might get. I know that there are some on here that will say "so what if your innocent you have nothing to worry about" I am, really, not so sure that that is the case in this day and age with the police.
Pete