Hi,
This is the only marriage I can find for a William Hartwell:-
William Hartwell (otp) & Esther Cowley (otp)
23rd March 1834 at St Paul, Portland Square, Bristol - Banns
and there is this baptism:-
William Robert Hartwell - 14th January 1838 at St James, Bristol
Parents - William & Esther of St Paul
Occupation - Servant
Minister - RA Taylor
Sue