Hi Charz,
Perhaps William changed his employment between marriage and the baptism of James either that, or the marriage to Mary Flanigan is not your William.
Have you looked to see if there is another William and Mary with children in Bristol.
I feel sure that I have done some research for someone else for the name Seaman or Seymour but I cannot find it in any of my PM's. I will check my box of notes which have kept after looking up things for others, it may be in there.
My first thought, was that Seymour was the mother's maiden name, so have you followed that line of thought.
If I find anything I will come back to you.
Best wishes,
Elizabeth