Extract from BS 5839 Part 6 : 2013 page 18.
Based on these considerations, a typical fire alarm configuration might comprise smoke/heat alarms within each flat connected to the social alarm system. The provision of these ought to be in accordance with BS5839-6. A separate communal system will normally be necessary if there are communal facilities and/or internal corridors. This system ought to be installed in accordance with BS5839-1 for the appropriate Category of system (Category L4 or L5). No communal system is likely to be necessary in simple sheltered housing that, architecturally, is similar to a general needs block of flats with no communal facilities. If a communal system is installed, as a further enhancement, heat detectors, connected to this system, might be installed within the hallway of each flat [in addition to the smoke alarm(s) within the flat]. The heat detectors could be used as confirmation of a fire within a flat. Under these circumstances, it might be appropriate, according to the fire risk assessment for the premises, to evacuate adjacent (or all) common parts and, if appropriate, certain flats in close proximity to the flat of fire origin (or, in small schemes, all other flats). For example, this might be appropriate in the case of a sheltered housing block that does not incorporate all measures normally provided in purpose-built blocks of flats as the basis for a "stay put" policy. Where the communal system is also used to alert residents to a fire in their own flat, or in an another flat in close proximity, consideration needs to be taken of the necessary sound levels within the flats.
As been said before AB it not as simple as that, but I must take Kurnal's advice and check out Colin guide.