Hello Simon,
At the moment, this is what I see:
Free BMD
http://www.freebmd.org.uk/cgi/search.pl Sep 1865 Forehoe 4b 169
Robert Sweetman
Dec 1866 Norwich 4b 150
Robert Swetman
1871 has 3 Roberts (similar surnames) born 1862-1868 in Norfolk, living : Kings Lynn; Norwich and Wymondham areas.
1881 RG11; Piece: 1949; Folio: 94; Page: 30
Robert, 15 yrs son onf William and Alice - born Norwich
1881 RG11; Piece: 1956; Folio: 83; Page: 19
Robert 15 yrs son of James and Rebecca - born Wymondham
1891 RG12; Piece: 1535; Folio 18; Page 8
Rober Swatman 26 yrs born Wymondham is a lodger in Wymondham
Free BMD marriage - December 1892 Forehoe district Robert Swatman and Martha Ann/Marion Ann Tillett
1901 -Robert and Martha are in Wymondham with family
However, Maggie and the children are in Norwich.
So, if this is your family in 1911, I don't think your Robert is the son of James and Rebecca. However, a marriage certificate would give his father's name and also may give clues to his regiment.
What do you think?
You could send for the Kilkenny marriage:
http://www.groireland.ie/