Flies: Help me!

[nosleeptilever]

For the last 3 days we've come home to find 6 or 7 gigantic flies in our living room. This is totally bizarre and disturbing because we shut the door when we're out to keep the cat out.
I can't think where they're coming from. Our house is fairly small and we keep it pretty clean and tidy so I'm really stumped. Mice have recently been an issue with the colder weather so we have traps behind the furniture and have thus far caught 2. One ended up staying in it's trap rather too long (DH neglected to check that week) and we started to get quite a smell. Once found we disposed of it and disinfected the area, end of smell. Now I'm wondering if this could somehow be the source of the flies? We've been more regular with mousetrap checking so it's not a dead one but for the life of me I cannot figure it out.
Anyone had similar or got any ideas?

I found loads of them hibernating or resting inside my double glazing windows. I had to open all the windows I don't normally open and go around the frames with a dustpan brush. I am going to wipe them all down with Zoflora when I get around to it as I have found the smells deters them.

Good idea! I've never wiped inside the frames so that might be it. Thanks.

Sadly, that is not where they are coming from. Frames all clear! Anyone else have ideas? DH is coming home tonight to help with a massive deep clean of the room. Hoping that roots out the problem.