The family is on the 1841 census
Piece number 1776, Folio 452, Page 23
As well as Sarah Ann, there is a Mary Ann, 1 year younger, Could the later of the two baptisms for SA be an error by the vicar and it should be Mary Ann, but he wrote the mother's forename in error.
I can't find a baptism for a Mary Ann.
Neither can I there is this marriage
1 Aug 1859 Saint Leonard, Shoreditch: Shoreditch High Street, Hackney
Mary Ann West Clark age 22, school mistress
Father
John Clark occ canal lock keeper
Spouse Daniel Thompson
Witnesses John & Sarah Ann Clark in brackets says (the father & the mother)
Added 1861 c
Piece 1079
Folio 83a
Page number 27
Daniel Thompson 25 Head
Mary A Thompson 23 Wife Heybridge, EssexHarry Thompson 1 Son
Mary Thompson 54 Mother
Mary Ann West Thompson Age 24
Burial Date 8 Dec 1862 Chelmsford, St Mary The Virgin, Essex
Edit
Ada Mary Thompson Baptism 4 Dec 1862 Chelmsford, St Mary the Virgin, Essex
Father Daniel Thompson
Mother Mary Ann West Thompson