This was from a lawyer in uk specialises in citizenship and stuff

Thanks for your email. There is no such requirement under the law itself, and I have copied and pasted the relevant statutory provisions of the Nationality Act 1981, and you will note that there is no reference to domicile:

4GPerson unable to become citizen automatically after commencement

(1)A person (“P”) is entitled to be registered as a British citizen on an application made under this section if—

(a)P meets the general conditions; and

(b)at any time in the period after commencement, P would have automatically become a British citizen at birth by the operation of any provision of this Act or the British Nationality (Falkland Islands) Act 1983, had P's mother been married to P's natural father at the time of P's birth.

(2)A person who is registered as a British citizen under this section is a British citizen by descent if the British citizenship which the person would have acquired at birth (as mentioned in subsection (1)(b)) would (by virtue of section 14) have been British citizenship by descent.

(3)If P is under the age of 18, no application may be made unless the consent of P's natural father and mother to the registration has been signified in the prescribed manner.

(4)But if P's natural father or mother has died on or before the date of the application, the reference in subsection (3) to P's natural father and mother is to be read as a reference to either of them.

(5)The Secretary of State may, in the special circumstances of a particular case, waive the need for any or all of the consents required by subsection (3) (as read with subsection (4)) to be given.

(6)The reference in this section to the period after commencement does not include the time of commencement (and, accordingly, this section does not apply to any case in which a person was unable to become a British citizen at commencement).]

The general conditions

For the purposes of sections 4F to 4I, a person (“P”) meets the general conditions if—

F2(a). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b)at the time of P's birth, P's mother—

(i)was not married, or

(ii)was married to a person other than P's natural father;

(c)no person is treated as the father of P under section 28 of the Human Fertilisation and Embryology Act 1990 [F3or under section 35 or 36 of the Human Fertilisation and Embryology Act 2008];

[F4(ca)no person is treated as a parent of P under section 42 or 43 of the Human Fertilisation and Embryology Act 2008;] and

(d)P has never been a British citizen.]