We had to leave our dog in the UK when we came to Oz. It was very hard on dh & dd, but it just wouldn't have worked out. Dd was beside herself for a few weeks, always asking for him & I'll admit it was heartbreaking. But she slowly releaised that he was better there [with dh's aunt] than here.
Here they need quarenteen for 6 months, and Adelaide Quarenteen couldn't guarentee him a place. So he could have ended up in Melbourne, Perth or even Queensland! Which would have meant 6 months in a strange place, without visits from us etc.
The flight was 24 hours [broken, obv] but we had a 14 hour stop over. Way too long, IMO for an animal to be 'locked up' in a small cage.
He needed an lot of immunisations.
We were quote over 3k to get him here.
Alot of rental places don't allow dogs & those that do have strict rules that they have to be kept outside. Our little dog would have gone mad & whined day & night after being inside in the UK. This can cause your landlord to end your tenancy, especially if it is disturbing neighbours.
We were also told by our UK vet that the extreme heat here can affect the dog as it won't be used to such high temps [we had 38+ for 3 weeks in summer]. Not sure how true THAT is, but a consideration?
It is actually easier going back to the UK. MIL's friend just did it with a year old puppy. They were able to quarenteen him at home with them here before leaving. He was sent to LHR [they arrived elsewhere] so they had to fetch him. But they could do that as soon as he cleared customs & spent 48 hours in quarenteen. So if you did buy new in NZ, it is easy to get them back to UK as rules going that way are more lenient.