Hi Carole. Your thought that Mary might be James' second wife and possibly not the mother of Henry is something I'd not considered - if she was then she'd have been c 33 when he was born, c 37 when James was born and c 40 when Thomas was born based on her birth year of c 1791. That does seem a bit old, leastways the last birth but I have come across ancestors where the woman had children into her early forties. Your thought that there might be older children as well is also worth looking at again, I did so about three years ago and found nothing but there are more resources on-line now plus some of SFHG's records have been checked and formerly missing entries added.
Hi Jon. I had noted that marriage at Brighton but had discounted it as being 'so far' from Herstmonceux but in light of Carole's comments and your finding a baptism for Mary Tapp at Framfield certainly makes sense of looking into this again.
I'll look for earlier marriages for James and if I find one then look for a death of that wife.
I forgot to mention that I found a burial for James at Herstmonceux on 16 Aug 1865 92 y/o giving a possible birth year of 1773 though his birth year was recorded as c 1776, 1778 and 1781 in the 1841, 51 and 61 censuses respectively so his stated age at death may well have been well out.
I also forgot to mention that Henry's approx. birth year was recorded in the censuses as 1851-bc 1825; 1861-bc 1827; 1871-bc 1825; 1881-bc 1826; 1891-bc 1823; 1901-bc 1823 and 1911-bc 1826 so again all over the place!