remember some time in the late '70s / early '80s going to watch Judas Priest at Sheffield City Hall.

That alone fits the threads, but the support band were some lads from Northern Ireland (I think) called Mamas Boys. They played jigs & reels hard rock style and I remember thinking that summed up my life at the time. (I was in a punk band on, say a Saturday night, and rattling off traditional folk in the same pub on a Sunday night.....)