Just to say, we changed over our driving Licence from UK to WA and it was so easy.
You just go to the licencing office, and fill out a form, take passport and Uk licence, you do an eye test there and then, they take your photo, and you pay your money. There's not theory test and we got our licence within a week. They also give you a form (intrim drivers licence) which can be produced until you receive your card through the post.
The cost is $35 for 1 year or $111 for 5 years, plus an additonal $43.40 transfer fee