I've found another twist - a convent attached to a Nursing Home, all owned by the same religious body.
The Nursing Home is straightforward, the pre FSO approach to this area on this site seems to have treated the communal areas of the accommodation (corridors, toilets, laundry, dining and living room) as covered by legislation/guidance (Firecode most probably as it was a Convent/Hospital before becoming a Convent/Nursing Home) with fire doors, extinguishers, emergency lights and AFD/call points, but treats the bedrooms as private as they don't have detection or sounders (more likely to achieve the 85dB at the doorway at a push rather than 75dB bed head).
The accommodation is purpose built 1970's with bedrooms (not en-suite) off a central corridor to the first floor and a single bedroom and all the shared areas to ground, with access to the chapel and nursing home at ground and a fire exit through a tank room (!) on the first in addition to it's own exits.
Employed staff from the Nursing Home carry out maintenance, the alarm is one covering both areas.
From this thread it appears that to ignore the bedrooms is the approach although with the layout and doors I'd be wanting the bedrooms to have AFD even if not bedhead sounders (candles!), but the thread suggests I couldn't use the RRO for this, just the 'it's a good idea' line.