You will need ILR in order to get British Citizenship via registration under section 4(2) of the British Nationality Act 1981.
(2)A person to whom this section applies shall be entitled, on an application for his registration as a British citizen, to be registered as such a citizen if the following requirements are satisfied in the case of that person, namely—
(a)subject to subsection (3), that he was in the United Kingdom at the beginning of the period of five years ending with the date of the application and that the number of days on which he was absent from the United Kingdom in that period does not exceed 450; and
(b)that the number of days on which he was absent from the United Kingdom in the period of twelve months so ending does not exceed 90; and
(c)that he was not at any time in the period of twelve months so ending subject under the immigration laws to any restriction on the period for which he might remain in the United Kingdom; and
(d)that he was not at any time in the period of five years so ending in the United Kingdom in breach of the immigration laws.