Paul C. Dickie wrote:
I had a similar stench in my cellar, but this one was more of bad eggs
and rotting fish. Shortly afterwards, there was a mini-plague of flies
and bluebottles ...

That reminds me - we get loads (and I mean LOADS) of bluebottle flies in
our 2nd floor bathroom at the moment. It happened last autumn too.
Every time we take the children up to bath them, we have to spend about
10 minutes swatting them and getting them out of the window. They're
really sleepy and can hardly be bothered to fly. I can't see where
they're coming in from. And there's no smell of rotting birds, etc...

Any ideas?

S.