My next door but one neighbour has started flying a drone over mine and other gardens. It hovers over my garden at various heights and flies around the area doing the same. If it was just once I wouldn't mind but it's happened at least 3 times that I know of, and maybe more when I'm not outside to see it. I feel as though I'm being spied upon, and although I have nothing to hide it still feels like my privacy is being invaded. I know where it's coming from as I've seen it going down in that garden.

Is it reasonable for someone to do this?

What should my first move be? Do I just go and knock on the door? Or are there any other options?

The people doing it are Plymouth Brethren by the way, and I thought they were averse to such technical things?