Hi Bruce,
according to the West Middlesex Marriage Index, there is a marriage 14 August 1796 between a Thomas BOWBRICK and a Sarah BANKS, Fulham Middlesex. Could this be your man??

This MAY be your Thomas BOWBRICK in 1851 in Camberwell Workhouse aged 78 Labourer, a widower. Unfortunately, his place of birth is stated to be unknown.
A second Thomas BOWBRICK is living in Wandsworth, Surrey aged 59. He is stated to be married but is apparently not living with his family, as he is living with a Sarah HODGE who is listed as Head of the household. He is a labourer in a market gardener and was born in Twickenham, Surrey.
The 1841 census shows this second Thomas with his wife Sarah. He is listed as a Green Grocer born in Surrey aged 45, Sarah is also shown as having been born in Surrey aged 50. The important thing to remember with regard to the 1841 census is that the enumerators were instructed to round all peoples aged 15 or older DOWN TO THE NEAREST 5 years. This means that alsthough Thomas was listed as 45, he may have been aged anything from 45 to 49, so that the age difference may not be nearly as great as it at first appears.
Interestingly, in there 1851 census there are 3 Bowbrick men stating they are born in Twickenham Thomas bn c 1792, Edward bn c 1793 and Henry bn c 1896. I would expect them to be brothers, if this helps.

Regards

Lesley
Australia