43.—(1) Where an adopting parent takes leave under section 42 F80[he or] she shall be entitled, if F80[he or] she so requests, to additional adoptive leave for a period of 4 weeks.

(2) The adopting parent shall commence a period of leave referred to in subsection (1) immediately upon the expiration of the period of adoptive leave under section 42 and shall cause F80[his or] her employer to be notified in writing of F80[his or] her intention to take such leave—

(a) at the same time as the notification of F80[his or] her intention to take leave under section 42 (2) is given, or

(b) not later than 4 weeks before the date on which F80[he or] she intends to take the leave,

whichever is the later.