I'd be far more concerned that the flats only have a sounder off the common system inside and not a heat detector off it as well near the door to the common areas (as a minimum). If it has a common alarm & thus presumably a simultaneous evacuation policy then that is usually something not to the standard for stay put (compartmentation, lack of suitable common area smoke control, etc) so it's usually vital to sound the alarm whilst the fire is still contained & not yet fully developed in the flat of origin - the detection being a back up in case the occupiers of the flat of fire origin are out when the fire starts or forget to activate a call point.
Flats are not usually provided with call points (access and testing once a year for the detector is bad enough without adding a call point) however this doesn't mean they might never be appropriate - whilst there is a 'typical' minimum specification for an alarm system for simultaneous evacuation in flats it's down to the situation in a particular building as to what is needed and sometimes it's more - I've seen common systems take the place of the flats self contained LD2 system (using conventional zones with hush buttons or the addressable common loop with suitable C&E) or even, albeit rare, a common L1 system covering virtually every area & room, common or flat, in a building, due to the particular scenerio
