Why leave Australia? Still one of the best trips we've made in the eight years I've been diving was to Byron Bay. The water was 75 degrees, and I was totally comfortable in a 5 mil suit (and I get cold easily, and HATE being cold). The variety of sea life was astonishing, and the diving was actually pretty darned easy. The town is lovely, and there is a wide variety of places to stay, at various price points.
But of course, I have to offer my own experience . . . when I reluctantly agreed to learn to dive, I told my husband I would do the classroom and pool work in Seattle, but he had to take me to my in-laws' place in Maui to do the dives, because there was no way I was EVER setting foot in Puget Sound. It was too danged cold! (The Sound ranges from a high of about 12C to a low of about 8.) But I ended up liking my instructors and my classmates, and they twisted my arms and MADE me do my open water dives in the Sound. It was the best thing that ever happened to me! It turns out you can stay very comfortably warm in cold water in a dry suit with the right undergarments, and the richness of life in our local waters has kept me happily occupied for the last eight years.
Don't give up on diving locally. It just takes the right gear.
Totally agree with you. Plus Byrons accomodation is quite cheap as they get alot of backpackers.
The diving there has to be one of the most diverse and AWESOME on the east coast (apart from GBR).
If you intend on making a road trip out of it (save $$ on flights) theres great diving along the whole east coast that you could take advantage of such as Forster, South West Rocks, Nelson Bay, Broughton Island, Terrigal and Jervis bay to name a few in NSW.
Plus you could get away with a 5mm wetty (maybe a shorty underneath) during winter.
I'd save an overseas diving holiday for after you have been certified so you don't have to spend valuable holiday time in a pool as oppose to over a reef/wreck. Just my two cents worth.
Cheers
Mike