When I do work for LA the flats are treated as domestic, the communal areas as commercial as they fall under the direct responsibility of the LA, general maintenance of the flats is the responsibility of the tenant, being called out to replace damaged switches etc the council would bill the tenant, repairs in the communal areas was at the council's own cost.
That's how I see it,
Also the same with private apartments I service, if it's a collective of tenants chipping in then I treat it as domestic, if it's a service company then I treat it as commercial, as u am billing a company direct, and not an individual that has been nominated by the collective of occupiers/owners
How would you know who to bill then,?