Magnet Bay is a nice left hand point break on the Banks Peninsular. It handles small to 10ft surf and works best on a southerly swell. Magnet can be quite fickle but is a nice wave when it is working. Getting in and out can be a pain (literally) with razor sharp boulders. It's an idea to bring booties. Magnet is the easiest spot to get to on the Banks Peninsular so is ideal to avoid the crowds at the main Christchurch breaks.
Gore Bay is a beach break about 1.5 hours north of Christchurch. It is a pretty consistent sand bottomed break that works best on a good south east groundswell and an offshore westerly wind. Can be surfed on all tides but is better on a fuller tide.
Make sure you have spare gear because there is not a surf shop for miles.
Mangamaunu is one of the best breaks in the area and well worth a visit. It works best on a southerly or south east swell and a west or north west wind.
The wave is very consistent throughout winter but make sure you have your winter wetsuit with you.
Kaikoura is at the end of a deepwater trench which funnels the swell and ensures that the waves that do hit this stretch of the coast pack a real punch.
Mangamaunu can hold waves of 2m or more.