Byrne - John 1860. - 1915

I am trying to trace any information about my Great Grandfather John Byrne who died in an accident Otira, New Zealand in 1915.  We don't have a lot of information about him as he died leaving a large family and I have come across many brick walls in trying to find him.
what I do know is that he married Sarah Taylor in Westland in 1891, lived in Stafford, New Zealand, working as a miner and was Irish. Some family records suggest that he was born about 1860-1865, but it could have been earlier.  
I cannot find any immigration records of him arriving in New Zealand, so it's quite possible that he came via Australia or USA following the gold mines.  One clue that I may have is that my Grandfather, the second youngest was named Bagnal Percy.  I have not been able to find Bagnal as a first name anywhere and my father did mention a family story that Grandad was named after the area that his father came from.  I'm wondering if he came from Bagenalstown.  
I do have a couple of photos of him.  
I know John Byrne is a common name and I may be looking for 'a needle in a haystack', but any leads that I can get would be appreciated.