He was married Feb 12, 1812 at the Mageralin COI church. Both were living in the parish at the time, says the church record. Are you sure he was from elsewhere? I thought the church listed many of his children's baptisms. If so, he remained in the area. Jane Gregston was married the next month and could be a relative. Mary Gregston was married a little more than a year earlier. No parents were listed in the original records. All the Gregtons said they were from that parish. How did you link them to elsewhere?
There was some sort of history of Mageralin and Dollingston COI on-line called " ? ? ? Evening ?" It had who paid for church pews and therefore some very early family information. Does anyone know if the site mentioned Gregstons?