Hi David
Do we assume that you are looking at post 1901, Amy is at home with her parents and 5 siblings on the 1901
When was John born and where, it might give you a clue as to a possible marriage
She appears to be registered as Amy Isabel Barney 1881, have you considered she used her middle name.
There are only 4 Amy Barney marriages on
www.ancestry.co.ukbut none of the possible spouses appear to tie up with the names you have
Have you considered a marriage might not have taken place ?
regards
Louisa Maud