Giovanni is the Italian for John, is it not?
There is only one record in Scotland of a John Battista, a marriage in 1945. And the 24-year-old in 1911 is the only Giovanni Battista.
Maybe he decided to retire back to Italy? Have you looked for a death there?
John is indeed the anglicised version of Giovanni.
Thank you for the marriage reference.. I checked this one and he's a Di Battista, different surname

Also, my Giovanni would have been 100 in 1945. He was Italian but thats a stretch

I have some cousins in New Zealand who are direct descendants of Giovanni, one who started the long running Battista thread, and they did hire an Italian researcher. They were able to find his birth certificate, along with his two brothers (and two sisters) and their parents marriage certificate. No sign of a death certificate, certainly under his real name but as I mentioned he was very fond of an alias and there is no guarantees he would have returned to the same region in Italy. I am hoping to try and trace the line back there one day and maybe we will find he returned there. It's a difficult task however as they came from Cassino, which was flattened in WW2 and most records destroyed. I also think they may have been there for a short time (it is well known as a transient area) and definitely moved on prior to WW2 though as I have visited the area myself and trawled the cemeteries with not much luck!