Interesting. This is a long shot ...
My 3x gt grandfather was John Bull, born in England around 1774 (NOT in Middlesex per the 1841 census), and in 1841 was a storekeeper in an Insane Asylumn in London (Melbourne Lodge, located in Lamb Lane). He died in 1843 in Hackney on the 30th March. His wife's name was Sarah (maiden name is unknown). She may have come from Colchester in Essex per the 1861 census.
They had at least one daughter and 3 grand-daughters, all of whom emigrated to Australia.
If, by some remote chance, you have something I'll be eternally grateful. It's like looking for a needle in a haystack looking for John and Sarah in the London area.