Hi Daniel
With Granmother Iris Jones, why not start a new post focusing in on her, requesting help for her family and history. Have you ordered your grandparents' 1939 marriage to confirm details on her age and father's name etc.? Whatever you can add about what you know about her and her family will help those doing searches for you
With Arthur Herbert, still struggling on him. Do you have any family stories for him such as was he born in SA or did emigrate there before 1910 and his marriage to Daisy?
The only additonal items which I can see (but don't not help further with Arthur) are numerous shipping manifest entries into the UK.
For example, there is a shipping manifest entry for him and Daisy arriving in the UK on 6 November 1922. A futher entry in 1938 for Daisy and daughter(?) Maryanne aged 21 arriving in the UK. Daisy shows as wife, so Arthur still alive at this time.
Arthur also shows travelling by himself on a number of crossings. None show his place of birth. His birth year seems consistent around 1887-8.
Maybe trying to find shipping manifest into SA would show his a native of SA (if not, show his place of birth)?. Findmypast
https://search.findmypast.co.uk/search-world-records/passenger-lists-leaving-uk-1890-1960 have shipping manifests to SA which might help. You need a subscription or credits to view details on there.
Monica