Revealing mistake: During the scene where the military loses control of London, and their snipers are told "all targets are free", you can see heavy padding beneath Infected/civilian victims' shirts, etc, as they're shot. Presumably it's to stop them injuring themselves when they fall over, or to hold apparatus for the blood effects, but it's too bulky to be part of the characters' clothing.
Revealing mistake: Fire proof gloves appear on Doyle's hands when he is on fire.
Answer: Nobody ever said they could only come out at night. As their food became scarce, they'd taken to daylight hunting as well.
Captain Defenestrator