A freeholder leases the entire property to 'A'. 'A' then leases out each individual property on separate leases (underleases). 'A' is then the landlord to those he has underleased the property to, not the freeholder.
The easy answer is to check the lease of the person who is asking (ask them to send this to you if you don't have a copy). Who is detailed as the landlord in the lease? Is there anything in the lease that states that another company becomes the landlord after so long (some leases let the management company take over after all of the units have been sold because developers don't want to be involved anymore)?