I'm only posting this as background, as it covers the questions I was asking myself as I had a look for Sarah for you:
DEATH: Sarah COSTER, death registered Marylebone Sep Qtr 1841 - age 45.
Buried 26 Sep Marylebone, age 45
CENSUS 1841: Census agrees, Sarah Coster age 43 or 45 with Joseph 44
Neither born in County.
Children: Elizabeth 20, Eliza 15, Thomas 13, George 7, Martha 3 all born in County.
There is also a Tho's LANGLEY age 30 in the household, Not born in County.
HO107 - Piece 677/Book 2 / Folio 52/ Pg8
Indicates a year of birth about 1796-98 for Sarah PIERCEY, not in MiddlesexCENSUS 1851: the children Eliza 25, Thomas 23, George 18, Martha 13 are all with their sister Elizabeth who is now married to John Cooper, with 3 children, ( was hoping the youngers might have been with identifiable maternal PIERCEY related family - but wasn't to be)
HO107 - Piece 1490 / Folio 103 / Pg14
DEATH 1849: Other posts indicate Joseph COSTER died 1849, from Cholera (and that he had remarried Hanna Wheeler, nee Constable in 1846, after Sarah died).
THE CHILDREN: Couldn't see any PIERCEY witness names on any of the 4 London marriages found for 4 of the 5 children:
Elizabeth married John COOPER 1842
Eliza 'married' Charles CLARK, circa 1853 when first child born?)*
Thomas married Elizabeth WEST 1857 (Elizabeth Cooper, witness)
George married Mary Ann HARMER 1861.
Martha married William HAWKES in 1857
* Forum posts
https://www.british-genealogy.com/threads/8267-CLARK-amp-COSTER-St.-MaryleboneCheers
AMBLY