A roof over our heads

We had some problems with our roof a year or so ago and it rained on the wrong side of the ceiling. We had a new roof over this area about a year ago and it solved the problem apart from some marks in the ceiling where water had got between the boards. I was keeping my head in the sand but Alison was talking to a friend who recommended a builder. A woman. She came and looked at it about three months ago and said the ceiling had sunk a little - probably with the weight of wet plaster. She appeared today with a muscle man. When she took the board down it exposed the lath and plaster construction. When they'd got rid of all this I noticed a small nest (think it's of a solitary wasp of some sort) somewhere between a golf ball and a tennis ball in size. Couldn't resist cheating a little by adding it as an inset.