JAT

First time on here so please bear with me. I am converting a garage to study and storage area. The garage is a single detached one and I have a side door and have put a window where the door was. There is a partion wall 2/3 of the way down the garage (now a room) do I need to have a fire door and Fire retardent plasterboard as it is not now a garage? Building control say Yes I'm not sure