So the flat is FULL of them in the kitchen/living area, now they have inhabited one of the bedrooms on the same side, the other side of the flat is unaffected.
What is causing them? the place is clean, and the bins have been brought out. The flat above has been making suspicious noises.. and I heard a saw and drill being used the week before... should I be worried? I have these horror movie images of a rotting corpse in my head. Or could they be down to a change in weather? (IDK)

AHHHHHHHHH.