Kiwi Advice - My advice is go for it!
Dude, sounds like a great plan.
April/May/Jun are some of the best months for surf as its autum and you get the early glassy winter swells with warmish water ( Feb and Sep being the other two good sytandout months, tho anytimes a good time ).
Raglan's worth a trip - its not so bad in winter crowd-wise, try mid week anyway, the locals are cool as long as you are too.
Being from Taranaki ( tho currenlty living in your inland surfless city of Manchester! ) I tell you now - go there! You'll find a selection of spitting beach breaks, long peeling point breaks, rock bank/reef breaks, groynes, river mouths, the blackest sand on earth too - the absolute works. And best of all, small crowds ( some days you find yourself looking for a break with others out just for company! ), and an ability to nearly always find a decent wave, as you have coastline facing nearly all directions - its the big lump sticking out the West Coast of the North Island halfway down. I surfed with some brits in Portugal last year, and these guys spent about 2 years there! Pack your snowboard and 20 mins inland you could be scoring fresh powder too.
Go check the purenz website and look the place up. New Plymouth is the main city, Taranaki is the province.
And dude, its off the tourist trail, those who 'go' 'know', the locals are friendly, and NZ has enough sheep anyway - don't be one yourself!
Other places - Gizzy on the East Coast, the Corromandel if its on ( tho go anyway, its stunning ). Kaikoura rocks, Christchurch is not that great for waves, but Dunedin and The Catlins way down south fire some of the larger waves to be found. Fourtune favours the brave down there in winter. As far as the big four cities go, Auckland has the most to offer surf/workwise, Wellington doesnt get much waves, Christchurch is so-so, Dunedin is a treat.
Go hard dude!