It was not always strictly adhered to so there are always exceptions.
Remember back then most people could not read or write unless they were upper class or nobility. Even the clerks recording births etc were not all that literate and that is where you can get variations in spelling.
I heard tell of one Parish Minister who made a bonfire with lots of his records as he thought they were worthless. Silly, stupid man.

Sometimes we are lucky finding the relevant record, sometimes not unfortunately.
Sorry I could not be of more help to you but we all have our brick walls.
Happy New Year to you and yours.
Dorrie