Sorry Pennines - I know how annoying it is when that happens!
In 1841 there is a mother Margaret Webb with 2 children -Thomas aged 7 and Margaret aged 10 living in St Giles in the Fields -- the Margaret aged 10, MAY be the witness at that marriage. Margaret the mother is a Laundress -- no father present so may have already died.
This looks a good possibility for the family.
The younger Margaret may be in service at 15 Albert St, St Pancras in 1851, aged 20, birthplace Hackney.
And a marriage, 2 August 1854 at St Pancras Parish Church
Thomas George Batt full age bach brass finisher of Fitzroy Place. Father: John Batt, tailor.
Margaret Webb full age spinster of Albert St. Father: Thomas Webb, dead.
Witness 1: William Wright
Witness 2: [can't read this]