They’ve been a Scottish thing for at least 15 years! Source: I ate one in Edinburgh 15 years ago.
Scotland is the home of deep frying things that have no right to be deep fried. My English friends are alarmed when I tell them of the “half pizza and chips” we used to have for lunch. Half a deep fried pizza, that is.
My dilemma as a student in Glasgow (a long time) at the start of term when I had some money, Fish supper or deep fried Pizza & chips. With the mandatory bottle of Irn Bru.
Delicious but excessive consumption would certainly reduce your life expectancy.