What? Another insect?

And not even a nice special one, but some nasty looking small member of the fly family ! Yes,this is personal, because I've been fighting this one and its relatives for a couple of days now. They like to congregate in the family bathroom and it seemed like they were having a breeding good time. I've been trying to shoo them away with soap, with open windows, with bleach, with vacuuming and dusting everywhere and finally I had it with them and have reached for the unliked but potent chemical weapons. I think I'm winning, but I won't cheer too soon.
Today had me cleaning all the nooks and crannies of the bathroom, the toilet and the kitchen again, but still when I had washed and polished everything, and put new flowers in the windowsill of the kitchen this one landed on one of the new gerberas !