Let me take you through the research process and my reasoning and deductions so far, I hope I have not made mistakes, but looking at all facts and going through my process may help, if only if it is to show others how to reason thing through etc.
Be AWare, there are several people by the name of William HEATH living around Chichester and Porstmouth area who were born within a few years of 1854.
- Subject
William James HEATH, b 1854 Chichester Sussex.
- Parents :
William Robert O. HEATH b abt 1821 Guildford-next-Stoke Surrey.
Elizabeth GORE b abt 1826 Chichester Sussex.
- Siblings
Hannah Harriot (HEATH) NICHOLSON b abt 1850 Chichester Sussex.
Alice LOCK b abt 1856 Chichester Sussex.
Leonard HEATH 1859 -1880 Chichester Sussex. (died from TB)
Albert HEATH abt 1863 Chichester Sussex.
Olive kate WOOD abt 1865 Chichester Sussex.
Ernest HEATH 1867 Chichester Sussex.
99% postitive married to a Mary Elizabeth SMITH - Pancras 1877 QTR J. Vol 01b, page 287.
Possible daughter : Alice.
Possible Presbyterian
William is an elusive person, He appears in the 1861 census living at home aged 7. See Chichester Subdeanery, subdistrict 5, Piece 623, Folio 88, Page 17 schedule 99.
1881 is an interesting census which I call musical chairs census, as it seems through my entire family tree, just about every household is entertaining another family member.
Established Fact number 1: The NICHOLSON HOUSEHOLD with Elizabeth and Alice HEATH.
Hannah is now married to John NICHOLSON.They have no children, but in the census they have an Elizabeth HEATH b abt 1851 and an Alice M HEATH b abt 1879, registered as sister-in-law and Niece respectivly to John NICHOLSON. See Leominster Littlehampton sussex, Distrcit 1, Piece: 1119 Folio: 23 Page Number: 37
so who is this mystery woman? It has to be a woman married to a man called HEATH, obviously, we can rule out one of John's siblings, only other candidates has to be Hannah s brothers. Leonard died about same time Alice born, but Elizabeth is still recorded as married and not widow, recorded as Bakers Wife. I have also found no record of Leonard having been married, the death certificate places him at his family home and signed by mothers mark, which also suggests he never moved out to start his own family. Ernest and Albert too young to be married to her to father a child in 1879 they end up marrying sisters. The only logical candidate is William.
Established Fact number 2 : A William HEATH living in London with his 16 year old Sister in law, Florence SMITH.
Census St Mary Islington,Islington East. District 27, Piece: 1119 Folio: 23 , Page Number: 37
Could this be some kind of private school or just being rented out for kids to stay in? WIlliam is marked as head of house. Note: his occupation is Baker.
Established Fact number 3: Research into Florence, the sister in law.
AS Florence is Sister-in-law and too young to be married, it must mean William is married to her sister.
Located Florence in 1871 census, Chelmsford, Essex,District 7 Piece: 1662 Folio: 121 Page Number: 1
No sign of Elizabeth, however going back to 1861 census,Chelmsford District 8, Piece: 1079 Folio: 127 Page Number: 4.
the Smith family have a Mary (E) ? listed, correct age as well. The transcriber is certain this is an E and well its too good a coincidence? could this be the Elizabeth staying with Hannah and John NICHOLSON in 1881? Maybe!
Established Fact number 4:A Marriage Found.
After an eternity of searching, I found an entry for a William James HEath and a Mary Elizabeth Smith last week. Pancras 1877 QTR J. Vol 01b, page 287. The certificate arrived a few days ago, and looks like we have a winner. Only slight change was WIlliams fathers name, listed as Robert HEATH, however we know his middle initial is R, seems to avoid confusion William Senior is using his middle name. Another interesting fact, the marriage was married in the Goldington Chapel according to rites etc of Presbyterians. So looks like William is a non-conformist, oh joy!
Conclusion
William is indeed married to Elizabeth who has a child called Alice M, these two are staying with Hannah and John in 1881, William is in London with his Sister in law. After that, they dissapear from all records. Well appear to. So where are they? Over to you!
Thanks!
SO no wonder why none of my even basic searches registered in my mind that it was the family I was after, Castle looks nothing like Heath, so I may have seen this name but never bothered with it.
With Ancestry. I was warned by people that the search is a load of 
A few months ago I went through all the all the William HEATH's returned for the Wills and Administrations on Ancestry, I checked that off my "to do list" as I did not find anything conclusive, I have just done another search for this and it has now returned that entry with India found at top of list.. , that would fit in with my Emmigration theory as well. 