Hi Jimmy,
The "NX" points to his having enlisted in New South Wales Australia ("N") for overseas service ("X") during WWII. The National Archives of Australia have NOT digitised his records (Barcode 4627093). I am sure that the Australian War Memorial would be interested in following up for Lance Corporal MYLES, and they may have recent details of his next of kin. Currently the AWM's nominal roll online reads
http://www.ww2roll.gov.au/ Name MYLES, ROBERT HENRY
Service Australian Army
Service Number NX80730
Date of Birth 5 Jul 1903
Place of Birth ASPATRIO, ENGLAND
Date of Enlistment 29 Dec 1941
Locality on Enlistment HABERFIELD, NSW
Place of Enlistment PADDINGTON, NSW
Next of Kin MYLES, ANNIE
Date of Discharge 20 Jul 1945
Rank Lance Corporal
Posting at Discharge 8 AUST ADV WORKSHOP
WW2 Honours and Gallantry None for display
Prisoner of War No
You do not mention where/when you found his medals, but I am sure that they are significant to him or to his descendants, and ought to be reunited with the family.
It is coming up to Remembrance Day, so I will post a message on the Aussie Board with link back to this thread in anticipation that there will be lots of willing Aussie RChatters who may be able to help reunite these medals with the family or find a good place for you to donate them to.
Cheers, JM