I have been trying to sort this out for years as well. A George Bell married a Mary Watson at Holy Trinity on 19 Oct 1793 - they are probably this Sarah Bell's parents. George and Sarah's first son, Benjamin was christened in the Isle of Man in 1818 but the 1841 census shows that Benjamin was born in England. Presumably, they wanted him christened in IoM where the rest of the Greggors were living. But were they married? George was a cooper like his grandfather. Greggor is spelt all sorts of ways over the years but Bell should be fairly safe. Have you contacted anyone at Holy Trinity to see if the original records for circa 1816 are available? The search goes on!