How do you explain where your ancesters come from?

On my mother’s side her grandmother are from Cork in Ireland and her grandfather are from Cornwall in Britain.
On my father’s side both my grandparents are from France.
I tried to explain to a person that my ancestry are from France because when someone refers to his or her ancestors you normally refer to the ancestors from your father’s side and not your mother’s side. But than this person disagreed and said it’s the mother’s side one should refer to a person’s ancestry.