I know this will sound very strange, but I would like to thank the Spare Parts sales rep from Eagers Holden at Aspley.
I phoned up requesting a power steering hose for my VY, and happened to mention that I also owned an AU as was having issues with it.
Turns out he was an ex-cabbie, and spent the next 20 minutes, in detail, explaining how to fix every issue I was having, and diagnosed it perfectly! All this and I was only buying a $15 part. Top service considering they're the competition