Oh you are all absolutely fantastic - thank you so much for your finds!
Looks like Joseph's MMN may also be 'Davison'. Haven't been able to find a Harry or Harold so could be a middle name? Will see if their daughter-in-law remembers anything.
Re Joseph D who died c 1974 where in Northumberland did he live?
Nothing obvious for death reg that year in NBL.
Only 1 born 1880
Don't know for certain but marriage is registered in North Seaton and he worked at Ashington (no dates given).
Can you clarify what you mean by "he permanently left England over 50yrs ago"
My grandfather married, had children and relocated to New Zealand 50 years ago. I don't believe he has been back since and don't believe he has maintained contact with anyone other than his brother.