In this Act "building control authority" means—
the regulator, in cases where section 91ZA or 91ZB provides that the regulator is the building control authority;
the local authority mentioned in subsection (2), in any other case.
That local authority is—
if, by virtue of regulations made under section 91ZD (higher-risk buildings in Wales: local authority work), a designated local authority is the building control authority, that local authority;
otherwise, the local authority for the area in which the building is situated or the proposed building is to be situated.