I did notice a Mary Seller was a Witness at the 1825 London Marriage.
1841 Census has a Richard/Mary Seller + Children living in St George, Middlesex. Both born c 1801, NOT in County.
Trouble is I cant find any of them post 1841.
A William SELLER born c 1799 Shottesbrook, Berkshire is the only male I can find on the 1851 Census.
+ a Harriot LEAVER nee Seller born c 1814 Shottesbrook with her Mother Ann Seller c 1771 Basildon
Worth noting for future Ref.