Shopping in NZ is quite unlike what most UK ex-pats will be used to. Choice and range is not as huge, as you might expect from the geographical location of NZ and the much smaller size of the population, but there are a lot of good local products and stores.
Food shopping - there are essentially two main supermarkets brands across NZ; one of which includes the no-frills Pak'N'Save and the more upmarket New World, Foodtown and Countdown are one and the same and the Foodtown stores are gradually being 'rebadged' as Countdown. Consumer surveys usually find PaK'N'Save to be the cheapest option, with New World at the other end of the spectrum - they ultimately sell the same stuff. Local markets and roadside shops selling straight from the growers can sometimes be a cheaper way to buy fruit and veg when compared to supermarkets.
Take aways / fast food - like any other country on the planet, NZ has Burger King, Pizza Hut, Wendys, KFC, MacDonalds, Dominos and Subway, as well as the likes of Starbucks. There are a number of NZ chains also, Hell Pizza being one of the main local pizza chains.
Coffee - there is a huge coffee culture in NZ at the moment, especially in Wellington where they seem to love their coffee, so there is always somewhere to sit and get a decent caffeine hit and usually a good selection of snacks, cakes etc.
Clothes - this is where a number of ex-pats find themselves a little dissapointed, there are very few of the usual high street chains most folks would be used to as import tax on goods is rather high for NZ and there is not the market here to support firms setting up. There are some exceptions, such as main brand names like Levi Stores, Hush Puppies, Footlocker and Esprit. NZ does have a great range of outdoors, skateboard/surfing stores. Shoes are a general source of concern, being rather expensive when compared to the UK for good quality, every day shoes and with a poor range of products; it is advisable to stock up in the UK before coming across! There are a range of local and Australian clothing firms, such as Glassons, Portmans and Max for women and Hallensteins or Rodd & Gunn for mens clothing. The main department store in NZ is Farmers, which would be something akin to Debenhams without the high end quality products or designer concessions. Wellington contains Kirckaldy and Staines, oft refered to as locals as the local equivelant of Harrods, probably be people who have never been to Harrods! Auckland has Smith + Caughey on Queen Street, you might recognise the many similarities with the setting for 'Are you being served?'.
There are plenty of boutique/local designer/designer stores, Paris Texas stock a range of clothing from a selection of labels for men and women.
Sports - Rebel Sports are the main chain across NZ, also R&R are another local firm with a few stores across NZ. There are plenty of outdoor stores as you would expect in a country obsessed with the outdoors, selling local brands such as Icebreaker, MacPac, Kathmandu, Swazi and Fairydown. Though some products are pretty expensive when compared to the UK prices.
Random - The Warehouse (where everyone gets a bargain) is an NZ institution, where you can buy almost anything and everything (depending on the season) from milk to perfume, clothes, toys, gardening and camping gear. K-Mart is also here and is a similar kind of store.
Housewares - Briscoes is one the main sellers of homewares, but you should only ever buy something from them when they have a sale on, no one seems to buy stuff at full price, but never fear they seem to have a sale on every week anyway!
Entertainment - books are very expensive in NZ, so stock up before you come and look out for offers and 3 for 2;s, better still join the library and find your local second hand bookstore! In Wellington I'd recommened Arty Bee's Books, 2 branches one at either end of Courtney Place. Local bookstore chains are Dymocks and Whitcoulls, while Borders now have stores in Auckland and Wellington.
DIY and hardware - Super sized warehouse stores such as Mitre10, Mitre10 Mega and Bunnings supply everything you can think of and more, from plant pots, garden and indoor plants, garden furniture, BBQs, home maintenance and building materials, power tools, paint, screws, kitchen sinks and everything between and beyond. Would be cross between Wickes and B&Q.