Well I have to stick up for Norma, 'cos she's from Hull too. Not that Norma can't stick up for herself.
My introduction to traditional folk music was at the folk club that the Watersons started (Folk Union One at the Bluebell), although at that time the Watersons had stopped performing as a group. Norma was in the West Indies. Mike and Lal performed regularly, though.
So if you don't like Norma's voice, don't listen to it. But recognise that you may be in a minority, and also recognise what Norma has done for our music, and what a smashing person she is.
I have to confess that I always preferred Lal's voice to Norma's, but together they made a great sound.