yep, just go to the GP who will refer you to the right place. And get your referral in that day if you can, sometimes waiting lists can be a long time.
I am in the process of the same thing ATM (well, not tubes tied, but having Essure procedure, so still permanent birth control). It took about 5 weeks from the referral to the initial OB/GYN appointment, through the public system.
ETA be firm on what procedure that you want. I have had the BP and the ob/gyn want me to have the Mirena - and when explained that I have 5 kids, and now health problems from the last birth, and it HAS to be permanent, they are then telling me that I should have tubal ligation, which requires a general anaesthetic and is a higher risk for me because of health problems and obesity, it also has a longer recovery time than the procedure that I want. I had to be firm, and explain that I understand the different procedures, and I am 100% certain in the birth control method that I think is right for me.