Fortunately, they got in touch this afternoon and are getting "their man" around tomorrow. Got notes, times etc in emails.
After further investigation, there are two panic buttons, one in the hallway near the door and one in a bedroom, but they have been painted over (what looks like several times) when the place has been 'refreshed' over the years. Probably fitted years ago by a old owner. We haven't touched them, and since someone is coming tomorrow we aren't going to start touching them now! ?
Just puzzling to me why it would only happen in the dark at night, Cold temperature? Spiders?