2) Mary Linzee Smith is bap 1775 in Stoke Damerel, dau of Richard and Mary
3) Brinsley William Hewitson married Mary Hester Dering in 1815. Definitely a daughter of your Thomas and Mary, as says with consent of Mary Linzee Dering Widow the Mother.
There is also a Judith Harriet Dering baptised in 1805, who looks to be re baptised in 1830.
All the above with images can be found on FMP.