Hi Roderick
Afraid I haven't (as yet) been able to identify your particular MacPHERSON men amongst those who were in Southland.
Focusing on John MacPHERSON; there's seems to have been a number of them - a farmer / a publican / a fireman etc.

There was a John MacPHERSON at Invercargill c. 1883 who had a business "MacPHERSON and Co." which sold beer, wine and spirits, farming supplies. It seems though this may have been the same man who back in
1867 (at Invercargill ) was the owner of a ship and was also described as "a merchant, sole partner of, and carrying on business as, under the style or firm of MacPHERSON and Company". [That info sourced from a number of newspaper articles - PapersPast website.]
http://paperspast.natlib.govt.nz/"Southland Times" - 19 July
1867 - page 6 -- column 3
Of course if you have UK census information that shows your John MacPHERSON as being "elsewhere" between 1867 and 1883, then the above is not applicable.
There was also a John MacPHERSON carrying on trade in the boot and shoe business at Dee Street, Invercargill in 1891. ??
"Southland Times" - 18 September 1891 - page 4 -- column 1
[Advertisement for Premier Boot Depot. ]
But it does seem that someone from this MacPHERSON family was in Southland at least in August 1882.
see next >>
~ Lu