One cannot assume anything in genealogy that's for sure The IOM is so small that folks can come from any part of the island. Many did indeed stick close to home especially in the earlier times but you can't always count on it.
The marriage usually took place in parish of residence of the bride but again that isn't cast in stone.
Many of the couples from whereever, went to Douglas or Braddan for the marriage.
The marriage record often gives the parish of residence of each the groom and the bride.
Who specifically are you looking for?
Donna