The police in the UK (as with much of the world) are frequently licenced to do things that are forbidden to the rest of us. Furthermore anyone trying to make a complaint or bring a claim in the courts against the police is likely to be met by stonewalling and coverups. You will need to have a very good barrister acting for you if you want to win.
The police are going to operate their helicopter wherever and whenever they like, and talk about fire cover is not going to stop them.