The CFOA perceived insights document gives the following guidance:
Individual houses (family/single occupancy)
The Order does not apply to individual houses whether detached or terraced, which are in traditional format (individual bedrooms, kitchen, lounge etc) occupied by a single household as domestic dwellings.
Private Flats (including those over commercial premises)
Private flats (having fire separation and separate access and egress) provided on premises as living accommodation for the owner or manager is to be regarded as a single private dwelling and as such sits outside the scope of the Order. Where such separation is not provided, enforcing authorities should remember that the responsible person (with a trade, business or other undertaking) owes a duty to relevant persons (in the domestic premises) and should take such action as will best protect those relevant persons from fire. However, even where private staff accommodation is provided, article 31 may be applied to the whole premises including that occupied as private staff accommodation.
Whilst the Fire Safety Order may be rather woolly in the circumstances I described, perhaps the Housing Authority has primacy? Is the Housing Act any more helpful?