I own 2 flats in a converted house which is split into 4 flats. I need to change the main communal front door. I know the doors into the flats from the communal area need to be fire doors. But does the main front door into the communal hallway need to be a fire door?

If it is the front door that leads from the communal hallway to outside then it does not need to be a fire door, there could be a situation where a fire doors could be needed but that is very rare.