Welcome to Rootschat.Have you got the names of any of the children and have you found their birth registration on the GRO site as that would give you Eliza's maiden name?
Welcome to RootsChat! Have you tried the Forest Of Dean website?www.forest-of-dean.net
The GRO Index Search has had Mother's Maiden Name showing for just over a year This will be shown for almost all births between 1837 and 1916.
Oh dear - they were in Monmouth on 1901, so this could be the youngest child's birth, but it isn't a lot of help as it gives his mother's maiden name as Johns!JOHNS, MARK mmn JOHNS 1898 M Quarter MONMOUTH Volume 11A Page 24