This question continues to be intriguing. Perhaps there is a Henry Thomas that should be considered, although I cannot prove?
First, reviewing Thomas Thomas and spouse, Sarah. In Kent between 1790 & 1807, there were only two entries recorded in England Marriages between couples of this name. Unfortunately RC & non conformist marriages cannot be traced. Both entries were 1800: Widen the search throws up couples throughout the UK, with a number in the East London area.
The Kent marriages, Thomas Thomas and Sarah Styles, 14 July 1800, Lower Halstow, and a later marriage of a TT to Sarah Beale, 29 December 1800, Maidstone, All Saints.
I keep coming back to review the 1841 census of a possible Henry Thomas, living in Northfleet, Kent with his wife Charlotte and a number of children. His birth is listed as c1801. The Ancestry census lists his name as Joy, but that is a transcription error. This is the 1841 census:
Joy Thomas 40
Charlott Thomas 40
Wm Thomas 15
Mary Thomas 15
Masha Thomas 15
Ann Thomas 11
Eliza Thomas 7
Amelia Thomas 6
Henry Thomas 13
William Clack 16
This Henry married Charlotte Beaumont 14 September 1817, Ifield, Kent.
Deaths of a Charlotte Thomas are noted in 1847, Faversham, and 1850, North Aylesford.
In 1851, Amelia can be found continuing to be living in Northfleet, with siblings. Ann is noted to be head of the family. Other searches In 1851 reveal no trace of Charlotte or Henry. Perhaps worthy of further research?