Thank you both so much for your prompt response. Still confused though. I think there must be at least 2 James Scadding's and / or confusion with the maiden name of James' wife/Walter's mother.
I have a copy of Walter's Death certificate - he died in NSW, Australia 2 June 1896 and that says his mother was Eliza Coombs. The informant for the certificate was Martha, his wife. Maybe she did not remember his mum's maiden name too well.
I also have their marriage certificate, 6 April 1881, from Victoria, Australia. That says Walter was a widower since 1875 and born in Guernsey.
On the marriage cert his parents details are given as James Scadding, Cabinetmaker, and Iset Scadding (Holmes).
I think that Holmes might be the more likely one, just because Walter was more likely to have given the details on that one rather than Martha.
Maybe Walter's mother was born in the Channel Islands? It's a bit confusing at times I find
