I think the bees are securely shut out of the house - fingers crossed.
After hoovering around the beams in the corner (interestingly they don't seem to mind hoovering, just banging they don't like) we could see where the holes into the wall were.
Having been sent to the DIY shop - yes we can walk to the local DIY shop! - to find a new bit for the toilet in the rented house, I asked the lady owner what she would recommend to block up the holes. After an urgent 'it's not Asiatic hornets is it?' we, and a man that was also there, agreed that if we squirted expanding polystyrene mousse into the holes that should do it. And they wouldn't eat their way back through.
So we did, and it seems to have done the trick for the moment at least.
I also managed to get into the conversation which house we had bought, that we were English and that we were planning to live here all the time. Much smilier after.
Note to self I am 'anglaise' with a 'z' on the end. I automatically say anglais which is French man. Ho hum.