General Register Office UK (GRO) Online Index to Births Deaths Marriages
Search the GRO historical birth and death indexes and order Certificates/PDFs Online. You need to Register and sign in, it is free. The GRO's indexes also contain for births the mother's maiden name and for deaths the age at death which can help you identify which certificate to order. This information is not available on Ancestry or Findmypast or FreeBDM. For information about what is on the certificate and how to set up an account etc see the link on the Right hand side "Most customers want to know."