Hi, welcome to the forum
.
You're right about the Unmarried Partner visa - not many people can qualify for it... it's either for people who have lived together abroad for at least 24 consecutive months, or for people who are both living in the UK (i.e. she has a work or student visa) and have lived together in the UK for 24 months.
You mention the fiance visa, but what about just getting married abroad and then applying for a spousal visa instead, thereby skipping the need for a fiance visa altogether (the fiance visa does not allow her to work or study in the UK, and it gives no NHS access).
For example, you could move to New Zealand together, get married in New Zealand when you're ready, and then move to the UK, getting her a spousal visa to join you.
That way you don't need to live together for 2 years, and you can save yourself a visa application (by skipping the fiance visa) - it would save you about £800 (or more) in visa fees.
Be aware though that all the family-related visas require you to be earning £18,600 in the UK - whether you apply for a fiance visa, spousal visa or unmarried partner visa, you MUST meet the £18,600 requirement.
You can meet it either by:
1) moving to the UK ahead of her and working in a job paying £18,600 for at least 6 months... after this, she can apply for a fiance or a spousal visa (or unmarried partner)
OR
1) securing a UK job offer paying at least £18,600 and starting within 3 months of moving back to the UK
AND
2) proving you have earned at least £18,600 in the 12 months immediately prior to submitting the visa application, either abroad or in the UK