Very tough and difficult to break up mass of silk cocoon found inside nestbox.Filling half the box.
No interactions present.
I would think it is more likely to be a wasp or bee nest I get them in my nest boxes but from your photo would not like to say which one it may be.
Definitely spun cocoons not bee or wasp nest. Cocoons similar in size to wax moth.
I think it is what has infested my shed for several years and makes silk tunnels in cardboard boxes; no bees or wax anywhere near. The adult moths correspond to the images of this species.
That looks a likely contender.
Lat/Lng: 51.7, -2.8
OS grid ref: SO4510