If you can't adopt preventative measure, like window/door screens, then remedial action such as old fashioned fly-paper, swatting and citronella candles can help.
It's a well known fact.
The normal more-prevalent housefly is a PITA and continually pesters anything warm blooded, but the less common larger manic bluebottle type is the most annoying and hardly ever settles for swatting, so an electrified tennis racket air swatter is required for them.
Just make sure that you're never stranded on a deserted island and encounter their 'Lord'.
But when I get annoyed- I remember all the 1000s of birds of all kinds, swallows and house-martins, they sustain. Our wonderful birds would not be here to wake us to dawn chorus or to entertain us with their beauty and arial displays... make me much more tolerant of them.
Some of the flies here actually bite if the weather is changing fast.
We were at a bbq on Saturday (in that heat) and the flies became unbearable, attracted by the meat smell. I did the "vinegar" thing and flies vanished!
At home I also put a few sprigs of fresh herbs on the table - Basil / mints / Oreganum /whatever has strong aroma, and that also helps.
Given your description those cold blooded small nosferatu type flies, they usually splatter leaving abominable blood marks on swat. Their are different in composition to those splinter-draculi type which are much larger and difficult to capture.
What I would suggest is to remove all kind of rot and decay omnipresent in the household and hang garlic in two perpendicular corners of the room. Few drops of ammoniac and cinnamon might help to create better light emitting ray which form a cross to deter the horrendous insects.
Try it for a day or two but no longer, the invasion should subside after 24 hour first excellent results should be visible. Then collect carcasses and burn them. Do not forget to spread the ashes in all four directions. Otherwise they might come back!
A dish of water with some vinegar in also absorbs odours in house. I put vinegar in metal jugs of water on top of the Swedish oven in winter, does a double job, of giving moisture in the room/absorbing odours. And the vinegar does away with having kalk buildup inside the jugs.
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2chf for 5 i think at ottos, one for each room..
Weeeeell, according to Wiki....
http://en.wikipedia.org/wiki/Horse_fly
or as the little buggers are known here
The following is taken from your English Wiki link:
Masses of these are commonly known to be present in some vehicles on the road and usually can be located between accelerator and clutch