Emma have you considered a homesbirth instead?
For the amount you would pay on a 12 month waiting period for PHI, then another 10 months for pregnancy, plus any oustanding costs (which I am unsure of, but I know each little thing (epidural, peth, c/sec) tends to cost more) - that medicare may cover part of but that still leaves you out of pocket.

I guess PHI is probably not as much as a homebirth, but for being in the comfort of your own home, guaranteed continutity of care etc...?
Might be worth considering.