Hello Keith
Devizes for a birth place may not be a red herring at all.
If they might be Nonconformists (NC), Dissenters, Quakers or Jews, do you know if records of all the Devizes Chapels and Meeting places survive and if any Catholic Records have survived and if all are actually online.
Some early Nonconformist (NC) records don't survive and this is probably the major headache for some of us stuck, when we go into the period before the first Census of 1841. I believe NC, may be my problem.
There are specialist Libraries, like the Dr Williams Library, London; the John Rylands University Library Special Collections, Manchester and others, which have some manuscript records and printed items of NC.
Sometimes C of E Visitation Surveys name some surnames who are NC in various towns.
Just because a C of E Parish Church married them, or buried them, doesn't always mean a C of E /Anglican Baptism.
Do you have their burial information and if any grave Memorial Inscription (M.I.) survives?
Surviving Wills and other documents, Tax, Land (Manor) records and Tithe Maps with Apportionment Schedules which list Owners and the main Occupier (not always helpful if the Occupier sub-lets), Enclosure Maps and Awards, can be good sources that might prove a family surname was resident. Early 19th Century Voting Polls if they owned property.
"
Devizes was a hot bed for dissenters." Bit more here about the various Nonconformists (NC) in Devizes.
http://www.trustfordevizes.info/the_dissentersMark