The resolution of this search came about after a number of small threads came together to present the full picture. A little bit of luck also went my way.
1856 T-CPL Michael James Fitzgerald originally enlisted with the 3rd Light Horse Regiment. His service record doesn't provide much detail about where he served but it would appear that he transferred to the field artillery as a driver and ended up in France.
I couldn't find any evidence that Fitzgerald married so my search extended to his siblings. After a false start in March this year I revisited the search yesterday. Fitzgerald was one of 13 children, one sister was Bridgett who married Reginald Roy Shanks. I found an interesting story about a deserter that Shanks was sent to arrest.
It is through Bridgett's family that I focused my research. Reginald and Bridgett son was Gerald who in turn had three children. As luck would have it I found a family tree which provided me the name of his daughter and who she married. This name is quite unusual and I could only find one similar on line. Taking a punt (yet again) I called this person and sure enough I had the right family. The lady I spoke to is Fitzgerald's great niece and I'll send her the medals in the near future.
Thanks goes to Ken Duncan who sent the medal to me originally.
The returned medal tally is now 1404.