Many thanks to all for all these very helpful facts.
I am sure that Caroline BURGESS was originally Caroline BOUCHER, and that she was a sister of Sarah Ann BOUCHER who married Richard CANDY in January 1837. Hence the two nieces - Sarah CANDY and Harriet CANDY - who stayed with her in various censuses.
I was hoping that in one of the early censuses her parents or other relatives may have been with her; in fact the 1851 Census is intriguing because there is a 57 year old woman named Sarah BOUCHER living with her, who could well be her mother.
If anyone has any inspirations, and in particular if anyone can identify when and where Caroline BOUCHER married William BURGESS, I would be very grateful of the additional help.
Kind regards
Philip Candy