Barm was always barmcake when I were a lad. So in Manchester it would have been a bacon barmcake. Barm' was an occasional abbreviation from over-busy shop workers.

As someone who's travelled around some with work this can get confusing real quick. You just want some sort of bread with bacon, egg and black pudding on your way to work without recruiting an interpreter. That's quite apart from ending up in uncivilised parts that don't feel black pud is necessary. :)