My husband's grandmother's maiden name was Annie Lilian Headford born 1876 Bristol. From the family bible we can trace the Headford family back to 1806 to John Headford born at Enmore. I would be grateful if you could let me know if your William Headford born 1750 is related to John Headford. Unfortunately I'm unable to help you with your missing marriage date.
Incidentally, John's wife Mary was born at Broomfield 1809.
Thanks for any assistance you can offer