Glad to see we covered everything if not a bit more! We also did the south coast of South Island from Dunedin round to Riverton and then up to Fjordland (saving the best till last!)Hi,
The sand flies are only a significant problem on the West Coast and Fiorland - and even then usually at dusk. Citronella insect repellant keeps them at bay.
If you are coming in late spring through to autumn I would go north from Auckland, maybe up through the Hokianga (kauri country) and through to Kerikeri/Paihia/Waitangi/Russell. From there you could explore the coast to the north which has some attractive beaches. It is along way north to Cape Farewell. If you do this make sure you drive to 90 Mile Beach -accessible via a good gravelled road. You can drive along the beach - even in a M/H. There are giant natural sand slides there.
Coming back down you have a choice of routes. The east coast is drier and the middle/west coast are greener. I think Coromandel is over rated - hard to get to the water at times - half of NZ thinks differently. I would probably go via, Raglan (worth the detour - great surf), Waitomo (glow worm caves) Rotorua, Lake Taupo (biggest crater lake in the world), Wanganui, Wellington. If you have more time add a loop from Rotorua around Poverty Bay through to Gisborne/Napier and back to Taupo.
For the South Island I would turn right at Picton, go to Golden Bay (a bit of a detour) and then back to Motuaka and down the West Coast to Haast - through to Wanaka/Queenstown and on to Fiordland. Coming back I would backtrack to Queenstown and then up through the Lindis Pass (middle of the South Island past Mt Cook) to Christchurch. From Christchurch there are a number of day trips that are worthwhile (Akaroa, Kaikoura (whale watching) and Arthurs Pass).
Trade Me website is the best avenue to sell your Motorhome.
If you have specific interests I may be able to recommend some attractions.
Regards
tony
saw Curio Bay and the Catlins.We found the landscape of Central Otago interestingly different.
Most of the New Zealanders we met said we would see more of NZ than they would,mind you we did do just over 11,000Km!