21.—(1) For the purposes of section 146(1) of SSCBA, a child or qualifying young person who is temporarily absent from Great Britain shall be treated as being in Great Britain during—
(a)the first 12 weeks of any period of absence;
(b)any period during which that person is absent by reason only of—
(i)his receiving full-time education by attendance at a recognised educational establishment in an EEA State or in Switzerland; or
(ii)his being engaged in an educational exchange or visit made with the written approval of the recognised educational establishment which he normally attends;
(c)any period as is determined by the Commissioners during which the child or qualifying young person is absent for the specific purpose of being treated for an illness or physical or mental disability which commenced before his absence began; or
(d)any period when he is in Northern Ireland.
(2) For the purposes of section 146(1) of SSCBA, where a child is born while his mother is absent from Great Britain in accordance with regulation 24, he shall be treated as being in Great Britain during such period of absence after his birth as is within 12 weeks of the date on which his mother became absent from Great Britain.