Many London register offices will no longer carry out searches or issue certificates for historical events. They will simply refer you to the GRO.
That is illegal report any that do that to the Registrar General and insist the registers are removed from the register office and the Superintendent Registrar be replaced as they are not carrying out the legally required duties.
The law requires:-
The 1953 Act for the registration of births and deaths in England and Wales
"31.-(1) Every superintendent registrar shall cause indexes of the registers of live-births and registers of deaths in his register office to be made and to be kept with the other records of that office, and the Registrar General shall supply to every superintendent registrar suitable forms for the making of such indexes.
(2) Any person shall be entitled at any time when the register office is required to be open for the transaction of public business to search the said indexes, and to have a certified copy of any entry in the said registers under the hand of the superintendent register, on payment by that person to the of the superintendent registrar of the following fees respectively, that is to say-..."
Similarly for marriage certificates:-
The Marriage Act, 1949
"65.-(I) The Registrar General shall cause indexes of all certified copies of entries in marriage register books sent to him under this Part of this Act to be made and kept in the General Register Office.
(2) Any person shall be entitled to search the said indexes between the hours of ten in the morning and four in the afternoon of every day, except Sundays, Christmas Day and Good Friday, and to have a certified copy of any entry in the said certified copies of marriage register books, on payment to the Registrar General or to such other person as may be appointed to act on his behalf of the following fee, that is to say :-"
Cheers
Guy