Help!! Plague of flies

[birdling]

We've been inundated with flies for the last two days. Huge black ones that are completely silent.
We haven't noticed any horrible smells.
They are fairly slow and crawl a lot, although they do fly around near the ceiling.
Have no idea where they are coming from.
Any ideas?

Eww, gross! I'm surprised they're silent if they're big? I was going to say they're probably cluster flies, as we've had problems with them in the past. They congregate in the loft and somehow work their way down. If you open your windows do they fall into the room? We had an exterminator in the end, though it was only having the roof repaired after the big storm last winter that they cleared off completely.

Could be. Haven't seen them coming in, they just appear.

Probably cluster flies. They will be coming in because it's got cold. They will just die off.

Another vote for cluster flies. Typically they’ve tried to hibernate somewhere (in small gaps in windows frames, for example) but they get disturbed. They gave quite a distinctive shape if you google them. Good news is they are easy to kill, bad news is they often come back every year.

Cluster flies aren't huge, they are really quite small.

Flies can get in through a myriad of places. I would start with pouring boiling water and then bleach down all sinks, baths and showers. Check your extractor fans for signs of fly poo.

If you want to get rid of them I got an excellent fly zapper from Amazon.

https://www.amazon.co.uk/dp/B017TDXN54?ref=ppxpoppmobappshare

Have you had any new houseplants? They are often a source of flies, the soil that is.

we had some last year, bought fly spray

currently have a spider sitting in its web in the kitchen, hoping that keeps them away