The Irish tinker thing is certainly not a myth. Her name was Ward and she started the second-hand dealership in Hull from a cart. The Wards are a long-established Gypsy family and we can trace our connections all over Ireland, with connections to the Quinns and the Briggs.
Don't know if Gran was an operatic singer, as sadly I never met her. I shall have to ask to see that photo though, sounds great.
From watching Travelling for a Living and talking to Mum, it seems that Hull was rather known for big singalongs in the pubs. We all like to think of a culture where we all sang together all the time anyway, but perhaps pub singing and Church singing is the answer?