I went to New Zealand in October/November. There was really a mix of weather. Rain and wind some days, beautiful sunshine other days. It was quite unpredictable really, but suffice to say I had an amazing time regardless of the weather.
Talking of buses, I took a Magic Bus trip from Auckland to Christchurch (http://www.magicbus.co.nz/main/produ...m?productID=94
- the New Zealand Encounter) and I would very highly recommend it. The guides were really friendly and helpful, and it was quite laid back. Not sure what you're after really, but this one has more of a relaxed vibe than what I've heard about the Kiwi Experience. There were people of all ages on our trip, and they catered for everyone's needs. It was good value for money as well. The only downside is that it misses a few good spots, which we overcame by renting a car for a week and going out exploring. But they do offer "add-ons" to the main trip, so you can see more.