sounds like a great trip you have lined up and sure you are going to love New Zealand.
Most people on our trips are independant travellers looking to join like minded people and experience as much of the country as possible. Many are also first time campers, though for most thats part of the fun.
Camping is in large, easy to put up tents with comfy mattresses. The big advantage over hostels is staying in gorgeous locations (though we still get big nights out in the cities) and having far more time to experience the local culture and hospitality - kiwis are a great bunch :)
You can upgrade to cabins on the way round and you will find a good number of people doing this throughout the trip. Its usually about £4ish to upgrade and you can decide on the day - so if the weather isnt great or you just fancy a solid roof you have got the choice - you will still be in the same spot as all the campers.
I agree with isabels advice too and its often great to take time to explore the best bits - we have 2 nights (3 days) around the best national parks and you can take extended breaks if you find somewhere you really like.
Hope this helps and feel free to ask any questions - however you decide to travel though have a fantastic time and make sure you do the dolphin swim in Kaikoura if you get the chance - always my favourite activity :)
I'm not really one for going on the piss every night (after a bad experience with an Irish bloke / litre of vodka / bottom bunk) ... so i decided to go with stray bus
There were quite a few Germans on there but also a few other nationalities like English and Irish and 2 Swedish chicks (the token Swedish girls!)
It was a nice mix of peaceful and seeing the real NZ as well as a few wines/beers on the night - well recommended!