Hi,
I have the Ashwell transcribed parish reocrds, and there are no baptisms for a John Cooper around 1784. There is a Sarah Cooper 11/8/1776, daughter of Francis & Mary, who married 1/10/1775 Ashwell - Mary's maiden name was Freeman. Maybe that is his family and he is missing from the records. More likely, he was born somewhere else and his family moved to Ashwell during his childhood. I couldn't find a marriage either but the Ashwell PRs only go up to 1812. Sorry,
Laura