Dry rot experiences?

[Ericaceae]

Hi folks. Anyone had to deal with dry rot before?! We came home to a literal mushroom growing out of our dining room wall, and I'm absolutely panicking (I'll put the pic in comments in case you're eating/squeamish).
Luckily I've got an estate agent and a solicitor pal, so they've put me in touch with trustworthy damp specialists who can come out tomorrow.
But I just see pound signs and mess

Finger for scale! (not envy)

Ericaceae, how did this pan out for you?

we had dry rot treated in house i used to live in (the cellar) job done quickly but my god the smell of the chemicals nearly choked me had to go out for about five hours

I am not sure this is dry rot may be more of a general damp problem.