Hello J.A.M.
Can I suggest you try making contact with fellow descendants through the White Pages telephone directory online?
There is only one Gardiner and four Robartsons listed in Merredin, only a couple of P. Lockleys and a handful of Horobins in Perth. Worth a try!
https://www.whitepages.com.au/residential (1) Jeanie b. 15 July 1900, m. Wm ROBARTSON 1924, d. 26 July 1976
(2) James b. 13 January 1902, m. Elizabeth Jane C HENDERSON 1928, d. 27 Jun 1978 as Jim
(3) Samuel b. 7 November 1903, d. 23 Nov 1976
(4) Thomas Hugh b. 19 May 1906, m. Kathleen M BIGGERS/DUNSTAN 1938
(5) Robert John b. 1908 (possibly Robert John b. Nov 1907 Larne Ire, m. Sybil J HANSEN 1943, d. 24 Feb 1998 aged 90)
(6) Sarah Campbell Gardiner b. 7 November 1909, d. 13 Nov 2002 [as GARDINER]
(7) William Gardiner b. 7 November 1911, ?m. Irene BAYLISS 1939, d. 11 March 1995
(8 ) Mary Gardiner b. 5 May 1914, m. Noel George HOROBIN 30 Jun 1944 [they had a daughter in 1945 and twin boy and girl in 1949, lived in Nangeenan], d. 18 Nov 1997
(9) Joseph b. 5 May 1914, ?d. 2 Nov 1989
(10) Lucinda 'Lucy' Victoria b. 1916, m. Thomas Chas Hugh LOCKLEY 1935, d. 7 July 2008
(11) Victor Gardiner b. 13 June 1919, m. Helen [Ellen] ZANETTI 1951, d. 24 May 2016 [aged 96!]
(12) Violet Gardiner b. 13 June 1919, ?m. Lionel D PRICE 1946, d. ?
(13) unknown Gardiner – born after 1923 [George, as per Welcome Wall post, most likely George S, b. 1924 Northam district WA, reg 144]
A George Stanley GARDINER b. 15 Mar 1924 in Merredin WA enlisted in Fremantle, next of kin Samuel GARDINER. Service number 30500.
Do you know who submitted their details to the Welcome Walls?
http://museum.wa.gov.au/welcomewalls/names/gardiner-sarah-williamDeaths from
http://www2.mcb.wa.gov.au/NameSearch/results.php and marriage from
http://www.wamarriage.info/