How exciting, where are you moving to? We're into a good summer so the winter weather will soon be a distant memory!
What plan are you on in the UK? We're separate companies but I'm sure we'll have something the same or very similar.
The SIM will be unlocked but would recommend we post it to an NZ address. We have 2 options re calling home - calls up to 60 minutes would only cost $2 - that's built-in to most plans. Otherwise there is an extra or Add-On (International Calling), which gives you 90 minutes for $25 per month, so depends on your calls.
Hope that helps. Click on my name if you want to message me direct with any questions.
Channel Manager, Help & Support Vodafone New Zealand