There are a couple of Fanny/Frances HISTEDs that could fit.
1. born 24 May 1797, bapt 13 Apr 1798, East Grinstead, parents James/Eliz
2. bapt 26 Oct 1803, East Grinstead, parents Henry /Mary
Think it may be the later as Fanny had sisters Philly and Lucy
Children of Samuel and Fanny from IGI, which match in with 1841 census except there was no William.
Henry bapt 9 Apr 1820 East Grinstead
George bapt 28 Apr 1822 East Grinstead
Samuel bapt 22 Aug 1824 East Grinstead
William bapt 21 May 1830 East Grinstead
Lucy bapt 14 Oct 1832 St James Croydon
James bapt 3 Jan 1837 St John the Baptist Croydon
Samuel who married Fanny was born in Croydon, according to 1851 census
Ian C