"8A. Persons ceasing to be exempt. (1) A person is exempt for the purposes of this section if he is exempt from provisions of this Act as a result of section 8(2) or (3). (2) If a person who is exempt – (a) ceases to be exempt, and (b) requires leave to enter or remain in the United Kingdom as a result, he is to be treated as if he had been given leave to remain in the United Kingdom for a period of 90 days beginning on the day on which he ceased to be exempt. (3) If – (a) a person who is exempt ceases to be exempt, and (b) there is in force in respect of him leave for him to enter or remain in the United Kingdom which expires before the end of the period mentioned in subsection (2), his leave is to be treated as expiring at the end of that period."
"284. The requirements for an extension of stay as the spouse or civil partner of a person present and settled in the United Kingdom are that: (i) the applicant has limited leave to enter or remain in the United Kingdom which was given in accordance with any of the provisions of these Rules other than where as a result of that leave he would not have been in the United Kingdom beyond 6 months from the date on which he was admitted to the United Kingdom on this occasion in accordance with these Rules, unless the leave in question is limited leave to enter as a fiancé or proposed civil partner; and … ."
"However, the Immigration Rules direct that a person seeking such leave is to be refused if they do not meet the requirements set out in the Immigration Rules … . This includes that the applicant has limited leave to remain in the United Kingdom other than where that leave is of 6 months' duration or less. Therefore you do not meet the requirements of having limited leave for a period of more than 6 months in the United Kingdom."