Pesky Flies!

Pesky Flies!

Observation - Pesky Flies! - UK and Ireland. Description: Overall length ca. 10mm; head and body, ca. 5mm. Very numerous, indoors. Nearly silent in flight but annoying due to quantity [perhaps fifty in room at a time]. Not especially attracted to domestic foodstuffs. Less annoying than common houseflies

Overall length ca. 10mm; head and body, ca. 5mm.
Very numerous, indoors. Nearly silent in flight but annoying due to quantity [perhaps fifty in room at a time]. Not especially attracted to domestic foodstuffs. Less annoying than "common" houseflies or blue/greenbottles, but I should much appreciate suggestions as to how to keep them away!