(1)The local authority may, at any time, extend the period within which any—
(a)work required by a work notice, or
(b)demolition required by a demolition notice,
must be completed by such period as it considers reasonable.
(2)But such a period may be extended only where the local authority—
(a)considers that satisfactory progress has been made in carrying out the work or demolition, or
(b)has received a written undertaking from the owner stating that the work or demolition will be completed by a later date which the authority considers satisfactory.
(3)The local authority must give notice of any extension in accordance with section 62.