Dear unklep,
I can't answer all the questions, of course, but can take an educated guess, as you might say.
Philip Henry Blackmore was born, according to the age on his death certificate, in 1832. I would think it more than highly likely that he was born in Cornwall. Blackmore is a not uncommon name in that part of the world at that time. It certainly is in accord with his being a miner.
The only Derbyshire county death of a Robert Blackmore in 1968, according to FreeBDM, was of a Robert K. Blackmore aged 74, not 84. Could well be him - surviving family aren't always correct in their memories of deceased parents. It would be possible to get more information if Robert's exact occupation during the years 1925 (say) to 1968 was known. He could be traced fairly easily.
The matter of his second marriage will probably be best discovered by yourself - if you have any family papers with names and dates to assist. For example your father and his brother's birth certificates would give you some leads. That part of your family history also connects with your question about why Robert and Phyllis separated - only to be answered within family memory, I would say.
There just maybe some NZ relatives. Robert's sister, Elizabeth Firth, had a daughter who became a Mrs Battersby. If you would like I could quickly check NZ births after 1930 and see where they lead.
Good luck in your digging, or mining!
