After reading ‘fire safety in purpose built flats’, I understand that it is not necessary to have a fire alarm specifically for the communal hallway but it is necessary to have fire detection in each flat. Therefore is it  ok to remove the communal hallway fire alarm?

many thanks for your help

If it's a purpose built block of flats built after 1962 and the compartmentation is still OK then a communal alarm is not usually required and can be counterproductive. If the premises have a automatic smoke control system (vents, shafts, etc) then you will need to keep the system to operate these (unless the smoke vents have their own detectors) but can remove call points and sounders.

If the premises are a conversion or in poor condition some form of site wide system may be required.

A competent Fire Risk Assessment should determine if you can remove the system, I've allowed this in several sites in my FRA