If the installer is a member of a Competent Person Scheme. NICEIC, NAPIT or ECA
The installer not need pre-notify Building Control and can start work immediately.
On completion of the works, the installer informs the Scheme operator (within 25 days) that they have carried out some work within a domestic property.
The scheme operator issues the Building Regulations Compliance Certificate to the householder/person ordering the work and the building control department within 30 days.
However, the installer must still issue appropriate BS7671 certificates to the person ordering the work as normal