Many, many thanks for your interest and your encouraging reponse, Dave. It all starts to make sense now. When my late mother and her two sisters talked (separately) to me about Ellen some years ago about their grandmother, the information was conflicting - and odd. The eldest sister said Simon Winter died, hence Ellen's remarriage. The youngest sister (who, with her family, had lived with her mother - Ellen's daughter - before she died, so may have been privvy to early family details) said that Simon and Ellen's marriage was annulled and that he emigrated to the US where he re-married and had twin sons. Annullment in those days would not have been affordable to the man on the street, so I did wonder. Then my mother said Simon was daughter Ellen's step-father. There may be some truth somewhere in the sisters' comments but it may be that, given the circumstances you indicate, they were fed diversionary information from their mother/older relations, to eliminate further questioning.
Simon was a tailor who worked in Whitechapel. Ellen was a tailoress. My mother remembered her 'Granny Crawley' who was also a tailoress, sitting with sewing. I note that the name Crawley was used, so, as you said, she used her maiden name (as she obviously didn't get married) and her daughter reverted to Winter on her marriage certificate to keep the records correct.
Another aspect which adds ammunition is that Ellen, the daughter, was brought up, according to my mother's sisters, by Mary Ladbrook who, with her husband, two daughters and one son, lived at 61 Sheridan Street in the East End. Mary is given as a 'seed sorter' on the census; later Ellen, the daughter, does the same work. Another Crawley/Crowley, Mary, lived there too, and is shown as age 77. I believe Mary Ladbrook was a Crawley too; records indicate she married Henry William Ladbrook in 1893. Ellen Crawley, the mother, appears as a tailoress in London, living elsewhere, so perhaps mother and daughter lived separately for some years.
The other strange addition to the Winter/Crawley saga is that Ellen (according to my mother and her sisters) also married Michael Crawley (when, I don't know). They said he was a sailor who bought a boarding house in Cape Town and later died there. A repeat of the Crawley name is odd or perhaps he came along first, they were married and Ellen took his name.
So far, I haven't been able to trace Simon, or his parents on immigration records and what happened to him is a mystery. I can't find any death records that seem relevant. It would be great to contact one of his descendants, so I shall keep trying, but any ideas/help would be brilliant. Also Michael Crawley, an apparently married man, heading for South Africa seems odd. There seem altogether to be too many red herrings. Thanks for your patience in reading this.