Hi Archiford
Welcome to Rootschat.
The parish registers for St Mary Newington are held at the London Metropolitan Archives and are only covered by the IGI baptisms 1813-1825, 1828-1837 and marriages 1813-1837
http://freepages.genealogy.rootsweb.ancestry.com/~hughwallis/IGIBatchNumbers/CountySurrey.htm#Nburials of course aren't covered by the IGI. The 1840s and early 1850s were when London churchyards began to close and have less and less burials as they made way for cemeteries as the sheer numbers of burials in the churchyards was causing a health risk.
There are very few people unfortunately doing lookups at the London Metropolitan Archives. London is a city of millions so there are always many requests for such lookups on the London and Middlesex board and from metropolitan Surrey on the Surrey board. The charges for searches at the LMA and at Southwark local archives which will hold microfilm copies of the registers are quite high and in the end purchasing the Newington death certificate, as that was where the family were on the 1841 and 1841 censuses, may be the easiest option.
http://www.southwark.gov.uk/uploads/file_6308.pdfOr, but it may be a long wait, eventually the registers will be digitalised and available on the internet.
http://www.cityoflondon.gov.uk/Corporation/LGNL_Services/Leisure_and_culture/Records_and_archives/Ancestry+digitisation.htmThere is no Daniel Brown marriage to a Sarah on Pallots marriage index for the right time and place.
The children's baptisms don't seem to be at St Mary Newington. There were two other Anglican churches in Newington - St Peter Walworth and Holy Trinity Newington which both opened in 1825. St Peter Walworth had a burial ground.
Regards
Valda