John Haynes, Shoemaker of St Briavels (General)
Seems possibly a little late but this looks like one of your Johns ?
"Morris & Co. Commercial Directory & Gazetteer of Saint Briavels 1876
Trades & Professions
HAYNES John, shoemaker, The Common."
Much more general detail abt the area in the full entry, here
http://freepages.genealogy.rootsweb.ancestry.com/~cbennett/stbriavels1876.htm
The definitive history of St Briavels can be read here, sadly no specific mention of your ancestors.
http://www.british-history.ac.uk/vch/glos/vol5/pp247-271
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