Fire Doors

General Discussion

I am looking at purchasing a buy-to-let and on my survey the below has come back;
"The property has four storeys of accommodation. The top floor is currently used for habitable accommodation. It is, therefore, very important to ensure a safe means of escape from the top floor and also the other floors. This can only be properly achieved by protecting the escape route, i. e. the landings and staircases, from fire or smoke which may develop in any of the rooms leading onto them. This protection can be achieved by upgrading the doors and frames to fire and smoke resisting standards. This work could be both disruptive and costly. Further advice can be obtained by contacting the local fire and rescue service."
Are there legal requirements around this? The property has period features including the internal doors.