We had a nest that started in the great hall, but you'd be surprised how fast they found their way to the ballroom, the dining hall and the billiards room when we didn't get them removed.

Seriously though, not all nests die off when left. I had one in the loft in my first house that was a few years old and left there untouched by previous owners. It had got so big over that time it had evolved from a standard hanging ball to fill in the gap between the roof tiles and rafters all the way into the corner of the roof. It was between 2 rafters so was essentially 2ft wide, 4ft deep and 4ft high by the time I said **** that and got someone else to remove it!!! It filled up 2 whole black 80 litre bin bags when removed. No amount of powder or spray would kill it off. In the end he just had to remove it by hand piece by piece.

 

I feel for you, mate. We had one that started in one of our workers cottages, before spreading to the chapel, the boathouse and eventually right across our whole estate...

That was when I decided enough was enough and got round to treating it myself.

I did take the odd precaution though:

 

Oh gosh, that sounds gastly!