I think to contact the INZ call centre in NZ is your only way to sort this out. Certainly the office and fees finder says London should be your office. However, recently, with some of the NZ offices having difficulty keeping up with the volume of work because there are so many foreign workers being taken on to help with the Christchurch rebuild following the earthquake, some NZ-based applications have been being processed in London. I suppose that could mean that what would normally have been London's cases to deal with may have, in their turn, been moved elsewhere.