Get a mortice with turn button on the inside. This covers the fire escape requirement though it does loose the option of deadlocking to prevent the burglars easy escape.
Personally I have one mortice with key both sides to lock when I am out. A mortice with turn button to lock if inside, and a key on the outside. Plus a night latch, to for general convenience.
They are all operated by the same key: as small as a cylinder type but with holes down the side rather than a serrated edge so kinder to pockets (Not so useful for opening parcels though).