Arguement with Holden service - advice please!

Hi all, looking for some mechanical and dealing with Holden advice. This prob is not with my 4wd but with my commodore sedan. It’s a 2003 VY v6 on factory dual fuel.

At about 45,000km it developed a rattle that was diagnosed as worn valve guides caused by the gas (according to Holden), they agreed at 52,000km to pull of the heads and fixed the problem under warranty. In the next 6000km I noticed it used a bit of oil and water, at 58,000km I checked the coolant level under the radiator cap rather than just in the overflow bottle – milky white oil under radiator cap – uh oh I thought head gasket. Back to Holden they tested it and say no leaks coolant must have been contaminated with oil when they pulled off the heads, so they flushed the radiator and replaced coolant and told me to monitor to next service.

In for 60k service today it has dropped the coolant below the add level again and there is evidence of oil in water again (all be it a fair bit less than before), Holden still say they cant get pressure tests to show the head gasket is leaking and want to do oil and water consumption reports and monitor it over the next 5000km. They think oil is residual from flush

All very disappointing since my last v6 did 240,000km when I sold it with only an alternator and water pump the whole time.....anyway

So my questions are this
1. How long do Holden have to warrant their work for (as vehicle is now out of warranty) and I do 600km per week

2. I was taught years ago if you pull heads off you should also drop the pistons hone the bores and re-ring or else you will always run into oil usage problems, do other people agree with this

3. If Holden agree to pull off heads again should I instead insist on a new long motor rather than be left with a motor in another 20,000 that is using oil and no chance of warranty? (My 4wd mechanic reckons I should)

4. What are my rights (I am in WA) as I can feel Holden slowly but surely shafting me

Thanks for your help