We are currently having the communal areas of our 5 floor victorian building redecorated. One of the requirements is a fire alarm system. We want hard wired throughout but are not keen on hardwiring the victorian foyer whose ceiling is 200 year old lath and plaster with delicate cornicing. We also do not want any wires to be displayed on the surface of the ceiling or walls as this would be totally counter productive to the appearance. Is there such a thing as a combination fire alarm system which allows for hard wiring and wireless?