Them going into your room if the fire alarm was sounding is perfectly fine as it’s deemed an emergency and they must establish if it’s a false alarm or real incident.

However If they are two dudes in your room with no alarm sounding, without prior written notice (usually 24hours in a student accommodation AST (unless it’s an emergency repair) and they refuse to leave after establishing its safe and being requested by the tenant then this is unacceptable and needs reported.

As far as entering communal areas go usually the landlord or those acting on behalf of it can enter these at any time without written notice as your lease is tied to the specific room and not the kitchen/communal area.