Hi, I did some diving in Bali in January. Can recommend. Nusa Pernida off south coast for some good drift diving also the wreck which is a shore entry of Tulamben. I dived with Tania Dive Cente out of Denpassar, I got the impression that you signed up with a DM and he fixes the other requirements - everyone sort of helps each other out, one guy has a boat, another provided rental equipment, another had a car to pick me up from my hotel etc. I did my o/w there. I was trainig solo and my DM organised a rescue diver to be my buddy and I was the only student those four days - You could wonder if this school was unpopular so had few clients but I found Wayan Sweta my instructor to be very thorough. Yes I did read the manual, yes I did watch all the video, fill in the knowledge reviews and complete pool training before being allowed to 12m only in open water.
Don't forget to haggle, I am almost embarassed by the amount of money I paid for such good service and a life changing experience.
As with most Asian holiday destinations I've been to the local people make the holiday, please take the time to make some friends. If you get the chance pop in to Krishna Bar in Sanur say hi to Madi and Suzanne from Neil, Keely and Giles.
For a terrific night head to Ubud for the Ramayana Ballet performaces of the Legong at the weekends - truely spectacular.
Have a great trip