Timbo, dunno if u know but sloes are the fruit/berries of the Blackthorn tree (similar to Hawthorn tree) often used for hedges etc, really easy to spot in the uk in early spring as the first tree to flower (a small white flower) before it has any leaves or any other trees have any leaves. No idea if u do have it in kiwi but we introduced most other prickly (well whins atleast) things so it would not surprise me.
Just thinking. Now may be the ideal time to look for trees in NZ (guessing ur just coming into early spring) usually march april time in southern scot not sure wot month that actually relates to over there
Still got a few places to try as well as my top secert bushes to try

they usually produce the goods, althou a bad year last year, a few on some bushes but not enough to pick. Still got a good few bottles left from previous years so won't go thirsty
Might have a wee experiment with brambles this year, like the sound of bramble whisky and might do a wee batch of vodka too, plenty brambles about
Slightly off topic but Is there any berries u can't use to flavour spirts?
Bumper year for Haws and rowan berries, i always thought both were fairly poisonous to humans but i think I'm right in saying u can make jellies/jam out off both. I'm no great cook so have never done it, sure folk do something with rosehips too?