Fire doors in rented house with 2 bedrooms

We own the upper 2 floors of a victorian house which was divided many years ago, and we now rent it out. There is a ground floor flat which we do not own, and then the door to our flat opens from the shared entrance corridor directly onto the stair up to the first floor, where the 2 bedrooms are, then continues up to the kitchen, living room and bathroom on the second floor. There are doors only to the two bedrooms and to the bathroom. Everything else is open plan. Question: as landlords, do we need to switch the existing old wood door from the entrance to the stair corridor to a fire door, to prevent risk of fire spreading from ground floor up to our flat?