Those hidden spots are absolutely worth the drive, but the water temperatures down South can be brutal even on a sunny day. Getting out of a freezing wetsuit in a cramped parking lot while the wind is howling is just pure misery. You can actually rent a car in New Zealand right here:
https://getrentacar.com/en-US/new-zealand . Just grab something roomy enough so you can comfortably sit in the back and change clothes with the heater blasting.