The house fly and its larval form, the maggot, is a truly domestic insect, so closely adapted to life in manmade environments that it is rarely found away from human habitations. The species, Musca domestica , is found throughout the world and is our worst pest among the flies. The larvae migrate to drier places for pupation to occur, and it is possible that your clean flat is on their migration route. Maggots are also commonly found on dead and decaying animals. Due to the meat embargo, there are probably huge caches of decaying livestock scattered about the country.
Most insect larvae are generic in form, hence the lumping of many species under the umbrella term.
More specifics could be helpful. A caterpillar is a larva, but with true and pseudolegs to aid in locomotion. Certain kinds of moths and beetles have larvae that are fond of flour products and often infest sacks of flour or oatmeal, or even spices that are stored away in dark cupboards. Dear AH, A short note to your reader who has recently experienced the joys and wonders of a front loading washer. One thing the Brits do have a leg up on us is in the realm of more ecologically friendly home appliances, which as Mark detailed, provide hours of home entertainment.