Hi there, I did Karate for many years about a decade ago and am looking to get back into it. I live in the Melbourne/Australia area and was wondering what the best style local to me is to try? Will I be able to start where I left off as a red belt?
Well, you won't - or at least shouldn't - start out again as a red belt, unless you go back to the exact same school as you used to train at, and you might want to have some proof as well (ex. your membership card from the JKA - IF your dojo gave you one...) if they don't remember you, considering you quit ten years ago. You'd be able to advance quicker than a new student nornally would if you decide to pursue a different style, however. There's no real best style for anything... I'd just recommend one of the four original styles of karate if you're aiming for traditional.
Every modern style of Karate has been developed within the past 110 years. Many Shodai Soke even had the same instructors. The many styles of Karate that we see are the result of different philosophies and personal tweaks on the same material. In the end, no Karate style is better than any other. The same is true of all martial arts. As for your second question, no. After a decade of inactivity, you pretty much have to learn everything over again.