I know this post was sometime ago and don't know whether you have found any further info. or are still looking....
I couldn't locate an exact match for Thomas BATEMAN born 1838 on the 1861 census either
This was the only Thomas BATEMAN I could find of the right age but totally wrong place of birth
1861 Vessel ‘Blenheim’
BATEMAN, Thos Single M 23 1838 Royal N C Voltr born Cork
I haven't yet managed to pick up Ann Helen / Ellen Glover on the 1861 census either.
This looks as if it could be Ann Helen/Ellen GLOVER on 1861c & possibly 1851c with her parents
1861c High Street, Wymington, Hamlet (Thomas LATHAM Head)
GLOVER Helen Unmarried F 20 1841 Domestic Servant Finedon1851c Harlock's Yard, Back Street, Finedon
GLOVERJohn Head Married M 30 1821 Labourer Finedon
Hannah Wife Married F 32 1819 Finedon
Ann E Daughter Unmarried F 9 1842 Scholar Finedon Elizabeth Daughter Unmarried F 7 1844 Scholar Finedon
Mary Daughter Unmarried F 5 1846 Scholar Finedon
Rebecca Daughter Unmarried F 1 1850 At Home Finedon
here's Thomas on 1841 which you probably already have, which links with the 1851 census you mention ie living with his grandparents Henry & Sarah ASHBY
1841 Nelson Street Middle Square, St Sepulchre, Northampton
HO107 Piece:814 Book/Folio:13/29 Page:13
ASHBY Henry M 45 1796
“ Sarah F 50 1791 Northampton
“ Dorothy F 5 1836 Northamptonshire
BATEMAN, Thomas M 3 1838 Northamptonshire “ Sophia F 1 1840 Northamptonshire
familysearch beta has this christening possible Dorothy above? Although she's dittoed as an ASHBY on 1841 census
Dorothy BATEMAN 12/9/1836 Ringstead Northampton
Father Thomas Bateman mother Sophia
and here's Thomas' grandmother Sarah on 1861 - shame he's not with her here
Both Thomas and Ellen's' address was No 10 Nelson Square, Northampton on the marriage certificate.
Thomas' father (also Thomas) was deceased and Ellen Glover's father was stated as John
Looks as if Thomas & Ellen may have been living with Sarah ASHBY after 1861 looking at the address given for their residence of marriage in 1862
1861 10, Square 2, Nelson Street, St Sepulchre, NorthamptonASHBY Sarah Head Widow F 70 1791 Formerly Washerwoman Towcester
plus a visitor & boarder