There does not appear to be a place or locality called Fernvale in Victoria.
I know that in 1954, he is on the electoral register in the state of Victoria (district: La Trobe, subdistrict: Croydon). He is living with his wife, Elizabeth, in Ferndale Rd, Mt Evelyn
Clara
The electoral roll listing for 1954 shows Fernvale not Ferndale Road.
Australian Electoral Roll
1949
DAVIES William Robert L 61 Blackwood Street, Yarraville Packer
there wasn't an Ian in his name
Clara
He enrolled with Ian in 1954.
1954
DAVIES Elizabeth 12 Collins Street, Melbourne Clerk
DAVIES William Robert
Ian Llewellyn 12 Collins Street, Melbourne Caretaker
1954
DAVIES Elizabeth Fernvale Road, Mt Evelyn Clerk
DAVIES William Robert S
Fernvale Road,
Mt Evelyn Labourer
A listing on an electoral roll does not confirm that the person enrolled was actually at that address on the day of the 1954 election eg the 1949 electoral enrolment for William at Yarraville was crossed out and Croydon and a date entered. He had also moved twice in the period before the 1954 election.
It would appear whoever gave the information for his South Australian death certificate may have confused the names.
I also find it a little odd that the cemetery can give you no further details from the burial register.
Perhaps your mother could make contact with the Victorian bdm's...email address on their website even if they would do a search between 1948 and 1954 for a marriage. Of course he may not have married Elizabeth.
http://www.rootschat.com/links/08jt/7.5.0 Children (applying for parent’s information)
7.5.1 Conditions of Access
In general, for children of the registered person to be granted access to information they must:
• For the marriage certificate:
Note - only a child of the marriage or one of the parties to the marriage will be granted access to the marriage certificate.
* Submit an application in the approved form,
* Provide reasons why they seek the information,
* Provide a copy of their birth certificate to verify they are a child of the marriage or that they are a child of one of the parties to the marriage,
* If either of the parties to the marriage is living, provide written authority from one of the parties to the marriage allowing the child to access the information along with three forms of POI documents from the party to the marriage. (Note: if no written permission can be provided the marriage certificate is restricted for 60 years after the date of marriage or after both parties to the marriage are deceased, whichever is the later); and
* Provide three forms of POI documents to allow BDM to verify their
identity.
Cheers
Cando