Ellen appears in the 1881 census for England and Wales, as a visitor of her sister Mary and brother-in-law Thomas (Jun) SUTTON, at Sibson, Leicestershire. She is shown as an Unemployed Domestic Servant at that time.
She has her 3 year old son Edward with her.
Thomas (Jun) SUTTON Head M Male 44 Sibson, Leicester, England Ag Lab
Mary SUTTON Wife M Female 40 Bambury, Oxford, England
James H. SUTTON Son U Male 21 Oldbury, Worcester, England Ag Lab
Albert SUTTON Son Male 10 Sibson, Leicester, England Farm Boy
Alice SUTTON Daur Female 7 Sibson, Leicester, England Scholar
Sam SUTTON Son Male 5 Sibson, Leicester, England Scholar
George SUTTON Son Male 3 Sibson, Leicester, England Scholar
Ellen KNIBBS Visitor U Female 32 Polesworth, Warwick, England Dom Servant Out Of Employment
Edwd. KNIBBS Visitor Male 3 Birmingham, Warwick, England
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Again, there is an Ellen Knibbs born at Polesworth who appear in the 1891 census, living at Bedworth Hill, Exhall, Birmingham. Warwickshire with the family of James Randle:
James Randle,Head,W,36,,Coal Miner,Employed,Exhall Warwickshire,,
Joseph Randle,Son,S,16,,Boatman,Employed,Foleshill Warwickshire,,
Sarah Ann Randle,Dau,S,,14,Scholar,,Exhall Warwickshire,,
Harriett Randle,Dau,S,,11,Scholar,,Exhall Warwickshire,,
Isaac Randle,Son,S,8,,Scholar,,Exhall Warwickshire,,
Emily Randle,Dau,S,,4,Scholar,,Exhall Warwickshire,,
Ellen Knibbs,Visitr,S,,37Polesworth Warwickshire,,

I note that James was a widower and Ellen was listed as a visitor. I also note from the 1901 census below, that Ellen's second son was born at Bedworth Hill shortly after the 1891 census was taken.
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Whilst it maybe coincidence, there is an Ellen KNIBBS from Polesworth, Warwickshire who appears in the 1901 census. She is given as aged 40 (this one would be 52 but ages were often given wrongly). She was living at Exhall, Warwickshire and appears to have another son James, aged 9 years, born in Bedworth Hill, Warwickshire.
Ellen KNIBBS, single, 40, Charwoman, Warwick Polesworth
James KNIBBS, son, 9, Warwick Bedworth Hill

An Ellen Knibbs died in 1906 at Exhall, with her age at death given as 54 which is reasonably close to the age that our Ellen from Polesworth would have been.

On that basis, I have drawn the conclusion that Ellen appearing at Exhall with a 9 year old son is our Ellen from Banbury.