Val
It good to hear that this subject is a straight forward question to you

I did a bit of research and I think I may have found the relevant bit in the legislation that states it doesn't have to be a workplace. I went on another forum where a serving fire officer says that if no one works in flats that are totally owned by the occupants then the common area doesn't need a risk assessment done, so there is confusion out there even by some professionals.
Duties under this Order
5. —
(2) Where the premises are not a workplace, the responsible person must ensure
that any duty imposed by articles 8 to 22 or by regulations made under article 24 is
complied with in respect of those premises, so far as the requirements relate to
matters within his control.
(3) Any duty imposed by articles 8 to 22 or by regulations made under article 24
on the responsible person in respect of premises shall also be imposed on every
person, other than the responsible person referred to in paragraphs (1) and (2), who
has, to any extent, control of those premises so far as the requirements relate to
matters within his control.
(4) Where a person has, by virtue of any contract or tenancy, an obligation of
any extent in relation to—
(a) the maintenance or repair of any premises, including anything in or on
premises; or
(b) the safety of any premises,
that person is to be treated, for the purposes of paragraph (3), as being a person
who has control of the premises to the extent that his obligation so extends.
(5) Articles 8 to 22 and any regulations made under article 24 only require the
taking or observance of general fire precautions in respect of relevant persons.