Hi Paul, It seems we are related. My grandfather is Arthur Oswald Diggins (born 1878) who is a son of John Emanuel Diggins and a brother of Percy and William Diggins. However I have different birth and death dates to you for John Emanuel.
I have two newspaper notices 1) an in memoriam notice which says John Emanuel Diggins died at Gaffney Creek on 6 November 1906. 2) and an article that says John was born at Tottnes, Devonshire in 1837 and at the age of 19 landed in Melbourne in 1856.
I also have a copy of his marriage certificate that has this birth date and place.
I have only just started researching the Diggins family. Do you have any other information about any of the family?