Mike, if its been raining heavily do not take your car down there. The ford you must cross will get you in trouble. On better days when the weather isn't an issue and the ford is low you can get a car in there and head right. If you head left you are bound to get stuck, unless you are 2 hot, blonde tourists in a station wagon that swim half naked and dance around a fire completely naked....Stop Neil, stop...omg.
As far as your car goes, you can get down to lake ferry mouth by parking in the carpark and walking down. There is another few spots you can access along that way such as the Whangaimoana carpark also. Use Google maps to find your way, or go there with someone who knows that area.
Te Horo is a hit and miss spot. It does produce monster snapper from the beach, and yes you can park your car there and walk down to the beach. The walk is quite short. Or you can do what Neil and I did and drive on in my 4x4, then get stuck in the tide and have to drive over a small gravel hill to get out. That was some entertainment.
If you really want to get out there it wouldn't hurt to go along to a WSAC weigh in and chat to some of the guys. They won't give you their hot spots (and nor should they), but they might be prepared to point you in the right direction.