I sympathise. I'm been having a huge problem with horseflies lately. I've been using 'Raid' in the blue can which is available everywhere. I just remove my animals from the room, wait until the fly/flies is/are near the window, spray then open the window and air out the room for a short while. It's very effective stuff so no need to spray lots of it.
I've also got one of those fly repellent boxes which contain citronella in the kitchen. It smells awful to begin with but afterwards you either get used to the smell or it goes slightly
but it's made a massive difference in the numbers coming into the house. It's gone from dozens to just the odd one (which are usually easy to catch and release back outside).
Also the sticky dangly for greenhouse things are brilliant. You just hang them up and boy do they catch a ton of flies. So much so that I feel like a mass murderer
I'm just so paranoid with flies around my bunny.
