If you regularly trade outside of NZ then consider opening up an online multicurrency account with your broker. I left ASB Securities since like you chaps I was paying a lot for forex transactions on each trade both ways (buy then sell).
ANZ Securities offer OMC accounts for UK, USA, and Australia.
I made a single forex transaction when setting one up for trading on the asx, and will only need to make another when I withdraw or deposit more funds. Meanwhile I trade to my heart's content on both the asx and nzx without incurring a single forex fee.
Check it out.
0800 805777 option 3.
BC