Not all of these suggestions will apply to your request but I have found actual birth dates given in some Baptismal Registers, in Non-Conformist records, in a family Bible, on the back of some photographs, in school records, in apprentice records, in some work records eg Railway employees etc., engraved on tomb stones, in newspapers (birth and sometimes death announcements or obits), and on some published family trees! Be careful of the last one because the baptism date is often entered as the birth date but it is possible that whoever owns that tree may have access to a document which isn't in the public domain and is able to help you.
From our transcriptions you will see that a James CURRY was baptised in Hutton in 1816 which narrows down his birth date. As the birth of a Sarah Jane CURRY was registered in the Sept qrt 1855 that should narrow her birth to the summer of 1855.