To be honest, we went via both estate agents and private and ended up getting a place via an ad in the paper (The Press). You'd "expect" to get a better standard of cleanliness etc if going via an agency but I know friends who have had awful experiences with agency rentals - so, it's a case of looking at both. Just make sure you have a Tenancy Bond in place if a deposit is required....
"The law requires that if a landlord or agent collects any money for a bond, it must be lodged with the Tenancy Services Centre within 23 working days of the payment being made, together with a Bond Lodgment form signed by the landlord and the tenant. A letter acknowledging the payment will be sent to both landlord and tenant.
The bond is held by the Tenancy Services Centre until the end of the tenancy, when either the tenant or the landlord may apply for its refund. "
Source:
http://www.dbh.govt.nz/housing/tenancy/bonds.html
Yes, you can find furnished. Not sure I'd bother shipping out items such as crockery or stuff that's heavy/bulky - the Warehouse is a cheap store where you could probably buy a dinner set for the cost of shipping one out from the UK!! Same with cheap saucepans, you can get them all at the Warehouse. Linen would be good to bring if you can.
Hope that helps...
Moorf