The UK General Register Office (GRO) holds a central index of all registered Birth, Marriage, and Death Certificates are a formal record of the death of a person, and typically include the date and place of death, the age or date of birth, and sometimes information about close relations. for England & Wales.
The indexes for births and deaths can be searched online for free via the GRO website, and as a bonus they included additional information for historical births and deaths.
For births, mother’s maiden names have been available on the indexes from 1911, these are now available prior to 1911 on the GRO index (where possible). This will be helpful to identify siblings in your families.
For deaths, the age at death in now available prior to 1865, which may help to identify your ancestor.
There is a useful tutorial at GRO Update – Searching the England & Wales Birth and Death Indexes.
The search dialogue does NOT support wildcards such as * or ? but it can be worthwhile trying ellipsis (…) which is used where the GRO indexers cannot decipher the name or part of a name.
See also the UK GRO Certificate Ordering service.Link: UK GRO Online Index Search