I believe the 'Hiton' written in the birthplace on the Census Summary for Ellen actually refers to her mother on the previous line.Great find Bert...
The location fits with being a mariner's wife, especially if he was still RN.
10 Cumberland Street, Southampton, Southampton, Hampshire.
The daughter could be one of these two. FreeBMD gave up only these for 1855 to 1857.... A year before the marriage too...
Births Mar 1855:
Fletcher Ellen - W Derby 8b 379
Fletcher Ellen - W Derby 8b 402
As for the 'any children issue', if Ellen's birth was registered it would worth taking a punt at the above 1855 births. Just enter the name and year but tick the No Box which asks if the GRO Reference is known. Then you can enter the parents' names. If the GRO don't get a match they will refund the fee in full.