Pejay,
Don't sell yourself short.
Why would someone of Faith A, use the church of Faith B for celebrating their bapts/marriages ?
In the era of early 1800s, the term "parish" referred only to a piece of territory served by an Anglican church.
But within that territory there existed churches/chapels of other religious denominations, including Presbyterians, Methodists Catholics, etc.
( See
www.genuki.org.uk... Northumberland>Parishes>Bamburgh)
Although English law, up to 1837, laid down that the only legal way to marry in England was in a church of the Anglican ("Church of England" ) faith.
But the law did not lay down that other denominations had to be baptised in C of E.
So couples of "non-conformist" denominations had to
a) marry in a C of E
b) not marry
c) marry outside of England ( e.g. Scotland) in a church of their choice.
But they could baptise their children in their " own" church.
And that is why I could not find Isabella's baptism in the Bamburgh "parish" register.
(People of Jewish or Quaker faiths were exempted from the law, and could marry in their own places of worship)
The Act was removed from 1837, allowing other religions to carry out marriages in their own church.
Michael Dixon