i can sympathise pap! My main bedcave is up in loft conversion in my gaff and one time i opened up window and like 10'000 flies come buzzing in! Turns out they is called "cluster flies" and they gather round window frames in sinister fashion waiting for victims!
I used to be ok with insects too, i mean except spiders who is bastards, but i felt that having millions of flies buzzing about would interrupt my sleep patterns so i sprayed like a full can of raid in there + closed door. They didn't like that, pap! It's pretty sick when they've been chemical weaponised and they do their mad buzzing death throes on floor!