???
Well here in WA my health fund, I only have to apply for hospital top cover, and waited for the 12 months waiting period and that's it, they don't even questioned about what type of surgery I am having... I don't know how it works in Melbourne, maybe shop around for other health insurance.. The only letter I got from my GP was a referral letter for the surgeon and that's it... He never wrote any letter to the insurance company.
But it maybe worth a try to speak to your GP and if he/she can write a letter to the insurance company explaining your situation :)
I am sorry I couldn't help you much... perhaps ladies from Melbourne will be able to help you better :)
XOX
Yools