I’ve come across quite a few small blocks of general needs flats (G-2) approx 6 flats. Where they’ve been built for stay put with a Grade D1 in place in each flat (not linked between flats) and a separate communal fire alarm in the communal lobby, stairs, corridors areas etc.

Im of the opinion that general needs blocks designed to support a ‘stay put’ policy, it is unnecessary and undesirable for a fire alarm system to be provided.
A communal fire detection and alarm system will inevitably lead to a proliferation of false alarms. This will impose a burden on fire and rescue services and lead to residents ignoring warnings of genuine fires.
Communal Fire detection may also promote evacuation into smoke filled communal areas. Any thoughts? 

Exactly the approach of Building Regulations and the current guidance - shouldn't be there.

If it's also activating the smoke control the system stays but sounders and call points go other than to any significant area of ancillary accommodation. If it's not then the whole thing goes - whilst the option to convert it to an Evac Alert System is there it's still a lot of additions and expense & with it being not statutory it doesn't get taken up.