I'm interested in whether the Seamans in Halberton in Devon were related to the Seamans in Milverton in Somerset (who me and Jacquie come from), but have had trouble sorting out who's who in Halberton. I think the grandfather of your Thomas was a John Seaman of Halberton b. 15/4/1737 bur. 18/6/1827, who is described as 'abode Ashbrittle' at his burial in Halberton - do you have the same?
Also, I have your Harriet Vickery b. 1814 in Stawley, not Ashbrittle, and can't see her in the Ashbrittle register?