Sdaiefk

As Kiwis you can enter Britain without a visa for a holiday for up to six months. Source: NZ MFAT

A standard visitors visa might be valid for a year but doesn't allow you to stay for a year. You'll need a different visa to stay longer than six months. Exactly what you need depends on what you intend to do. Check here

Of course, if you renew your British passport^* you can stay as long as you wish, but your wife will still need a visa for a longer visit.

^{* Strictly speaking, as a British citizen you should be allowed to enter without this, but expect to be held at the airport while your identity is verified. A valid passport is much easier!}

As I understand it.

You should renew your British passport and enter the UK as a British citizen.

Your wife can enter the UK for visits of up to 6 months without a Visa. There is no formal limit on the number of visits or their cumulative length, but there is a rule that one must not live in the UK through frequent or successive visits, so trying to get around the 6 month limit by making a "Visa run" is a risky strategy.

While the UK has visitor Visas of various durations the length of any given visit is still limited to 6 months and the rules about not living in the UK still apply. So they don't help you much.

If your wife is under 30 there is the option of a "youth mobility" visa which allows a stay of up to two years (and allows working in the UK during your stay), though you can only get it once.

Otherwise i'm not sure there are any good options, there is the "family visa" but that is intended for people who will move to the UK permanently, not for long visits.