I've only just seen your post chazza, but like everyone else am horrified to read what you have been through, especially as the front they use is squeaky clean, wholesome and unthreatening.
Yes, they must be reported as they could do the same to someone who might have heart problems with dire results. We are all told not to open doors to anyone during the hours of darkness, but it's an automatic reaction, isn't it? Not as scary as yours. but when I had 'odd' knockers-on-the-door at night my husband had a spyhole installed in the door. If this is feasable, might be another option.