Hi Anthony,
I'm in Australia too...
a couple of things... you mentioned Condon, but I dont know if he is part of your family.. if he is, I know a family in Australia who would love to learn about the family connection... they are in Victoria.
With your Mr SYMEOU
I have gone straight to the National Archives of Australia for a first stop.... because the British subjects have some records on the Australian archives too... I can see records for the family... there are at least 2 Georghios in the family... one born 1924, one born 1927 and being British subjects, I would assume they are born within British land. But there are a few records for people who could be siblings too, its worth looking.. Here is the link. IF the records have not been examined, you can request it.. they are free if you are willing to wait around 12 months, otherwise they will give you a quote (most look open but not online yet, so some are a waiting game... but there are a few worth looking at... entry to Australia especially... it has addresses).
https://recordsearch.naa.gov.au/SearchNRetrieve/Interface/ListingReports/ItemsListing.aspxI have checked the obvious free places like the Australian War Memorial and Imperial War Museum of the UK but nothing shows up for SYMEOU.
BUT.... the Imperial War Museum DOES have info on the Macedonian Mule Corps... and the surname shows up, just not when I search.
https://livesofthefirstworldwar.iwm.org.uk/searchlives/field/unit/Macedonian%20Mule%20Corps/filterI feel our servicemen have paid the price and war records should be free... whether they came home or not, they paid the price. My advice on getting the records for free would be try a free trial on FOLD3.... but before you sign up for the free trial, make a list of who you want to research... you will be able to download service records free from there... assuming the Macedonian Mule Corp is included.... should be because he was a British subject.
OR head into your local library, sign up for free and try to access the Ancestry library edition, which should give access to service records.
I know Find My Past has service records too... but you pay... unless you have a free trial....
I hope that lack of information helps you... sorry I don't have the records you want... but there may be a way around the $$$$$ that archives expect you to pay.
I am going to have a look tomorrow.... its after 10pm here and I am heading to bed.... need sleep. But if I don't reply, I will forget, .....
actually.... sign up for the National Archives UK (free)... there are some records you can 'add to basket' for free if you are signed in. they are pdf and may give you a little info. I just added one for another soldier in the same corp.. to my basket so will try yours tomorrow too...