This website gives you access to lots of info upto 1976.It may help locate NSW relatives.If you get your grandfather's death certificate it will give you his parents and his wife's name. He died on 3 Feb 1978 aged 79 late of Penrith - according to the Ryerson Index of death notices.
The only Reginald born in Sydney around 1900 was a Reginald P [could be T] born 1902 to James Malachi and Gertrude Clark. Reginald married a Ruby Pickering in 1922. I hope some of this sounds familiar...If it does, you can trace back for at least four generations and will eventually get back to Henry and Sarah [also known as Mary] Oxenham.Good luck!