Hi again,
I ran out to the library this afternoon for another look at the TAS pioneer index and also checked the TAS archives online but nothing looks too promising. These records show that the John born to John and Deborah was married to Sarah Lucas in TAS in 1867, assuming that is so we can rule that out. Not sure if this has any relevance but there is an Edward Payne and wife Georgina in the TAS records at the right time, a son Edward was born in 1822 in Hobart (my John had a son Edward) but this might not mean a thing!
I thought he arrived here before the first marriage but will have to check where I got that info from, as you say there seems to be no marriage record to Sarah Crane. There are a couple of John Payne's on ships to the mainland - one on "Ellen" in 1844 from George Town to Port Philip; and one in 1853 on "Helen's Page" from Hobart to Melbourne.
Their first and only son was born in March 1854 in Robe SA so the marriage took place between 1847 and 1854 by my guessing. His obituary says he went to Melbourne from TAS at the age of 18 and shortly after to SA. This could be between 1844 and 1850.
It is interesting that Sarah was 29 in 1855, perhaps he was in fact older and the earlier 1826 date not too far off?
Hopefully I'll get some sort of breakthrough! Thanks for your help so far

Kelly.