Yes I did think about Buniygong not be the actual place but someplace near pr the general area etc BUT I have looked into this thoroughly by contacting various historical societies and going through all the Victoria BDM's and there are no Kirker's there listed anywhere for that state.
Although we can never be 100% accurate because records do get lost and people do sometimes not get registered on any official documents so there is a very small chance that William was born in Victoria and just not listed anywhere. Strange though that there are no other Kirker's for the state of Victoria during 1800 to 1875 as I would have thought at least one of his parents or possibly a sibling might have died there etc. But no there are no Kirkers mentioned anywhere. Which is kind of odd.
This pretty much does make you think that he didn't come from there and perhaps lied for some reason. Maybe escaping a marriage or a crime or family?
We may never know.
I will definitely try to see if I can get a printout of his marriage and see if it has any extra information though I am not hopeful. I will ask around some of the other distant family members and see if they have a printout and what information is on it.
For now I guess this is a brick wall that will remain.
So far I have tried pretty much everything in New Zealand and Australia. Ireland was kind of my last hope...
Maybe one day
Thanks so much for all your help and suggestions.