kiwifolk is a good place to start.

We were in Wellington 2 years ago and did a house concert at the home of Ruth Birnie and Gerard Hudson (Musichaven). They're still doing those out at Paraparaumu.
There are singarounds at The Welsh Dragon Bar (Kent Terrace, Mount Victoria 6011) which claims to be the only Welsh pub in the southern hemisphere. The room used is circular, and use to be a toilet! It has a mural on the ceiling too. One of the blokes we met there is an ex-pat who was in a morris side, so you may get to dance yet.

Splott Man