Actually there are a lot of grass strips within a comfortable flight time of Wellington, and they can cater for a range of experience - from airfield (eg., Masterton, Martinborough, Foxpine, Flat Point) to challenging farm topdressing strips.
Things in NZ are probably still a lot more laid back than the UK. You can probably go to many private farm strips and all you need to do is ask.
Flying conditions will be challenging - WIND!
You have a good aircraft for strip operations but be careful, and don't be afraid to ask for some advice/instruction from some of the experienced (perhaps ag) pilots you should be able to track down.