Start with charters who will work the outside of the reefs. We used to hire a local cat from one of the villages, but they don't have the safety gear or VHF that the pros use. Land based is an option if you go with someone from the village where you expect to fish, or with a local who knows them. 

How did you get on Jonty.M?
I was watching some average size models smashing a good sized boil up under Aggie Greys Resort wharf last weekend! Impressive stuff just didn't have my rod