Thank you so much for all your time, you've given so much information! Very happy that one of the houses which the Browns lived in, in Deptford, is amazingly still there!
With a name like Hephzibar Claydon, it was pretty easy to find more information on her through Familysearch.org and Mundia.com. Her name was Hephzibah Ralling and was from Stambourne. From that I found her parents who were John Ralling and Bridget 'Biddy' Banks.
Thanks again Louisa, interesting though that this has proved that the Brown's aren't from actually from Essex (as previously thought). The furthest back for the Brown line would be Albert Brown born in Whitechapel, but we know his father is William Brown who was also a P.C. which should (fingers crossed) make it easier to search the census returns.
Should I post a new query for that information in the London and Middlesex board?
Kind regards
Miles