I have now sorted out Laura, Percy and eldest brother plus their mother, only one left now is Ivor so I am researching all avenues.
I have found Ivor on 1954 (with wife Martha) & 1958 ER in NSW (with mum, brother & sister, brother Percy is on same ER page in 1958), I have also found 2 Ivor's in 1977 and 1980 with a Beverley Dawn who is mentioned on the DN you gratefully supplied, and they were in Peakhurst. Of all the Ivor Jones's deaths found by a Ryerson Index search only two stand out, all others are of wrong age as Ivor was born late 1918 / early 1919.
I am hoping further research with surviving family members who are my distant 3rd cousins may solve my research, in the meantime I plod on.
There is another death in 1982 but again his age doesn't appear - I do know his "son's" name, he was born before Ivor married Martha in Blaenau Ffestiniog, and the son is likely to be her child from a previous marriage / partner or Ivor's before he placed the band of gold on Martha's finger. Later today I will order Ivor's UK marriage certificate for more detailed information.
The other death notice I found is below, and Punchbowl is where I found his ER record 1977 / 1980. I have also found his son in NSW in 1980 ER, but he may well have moved by now. It is a pity that Aussie records are not as open as our UK databases. I cannot confirm this 1982 death with the NSW Archive as they only allow current searches up to 1981
JONES Ivor
Death notice 17DEC1982 Death
at Kogarah, late of Lakemba, formerly of Punchbowl
Sydney Morning Herald 18DEC1982