Read your GMH warranty terms and conditions. The Holden dealers are designated by GMH for warranty work.
You must work through the dealer service network for warranty claims.
Many years ago, the manufacturers views and documentation were that service must be done at a dealer service department or you loose your manufacturers warranty. Such views were jumped on years ago by ACCC and those terms were removed from warranty documents. Now service can be done elsewhere while still retaining one's factory warranty.
More recently, manufacturer incorrectly viewed their warranty processes as trumping ACL (for all intents and purposes). Now we now know that the law has a different view on the matter and as a result Ford has been fined $10M and required to do certian corrective actions. Separately, Holden, Hyundai and others have made undertakings to ACCC not behave like dushbags when it comes to warranties.
So, I'd consider the fact that a manufacturer mandates warranty work must be done at a dealer only carries weight by virtue of it being written down on the manufacturers warranty documents. People believe such has the force of law behind it so in that sence it serves the intended purpose, however it's in the same vien as the above and likely does not carry much if any legal weight.
After all, did anyone sign an contract that stated they will comply with the manufacturers warranty conditions? My sales contract makes no such mention of any warranty conditions and in any case ACL trumps whatever would be stated (especially if some warranty conditions tried to removes ACL rights in law).
Put another way, just because it is written in some document doesn't make it have the weight of the law behind it...
Having said that, you'd have an argument on your hands if you wanted warranty work done elswhere. So unless you have solid grounded reason, correlated to ACL legistaltion, for requiring the warranty work be done elsewhere, and i can't think of one, then it's simpler to just go with the flow and do the warranty work at the dealer.
That is, unless you are willing to fight by requesting the selling dealer to pay for the warranty work at one's prefered place and then bring a case to your states Consumer Admininistration Tribunal when the dealer says 'no'... along with a solid grounded reason as to why you don't want the dealer to do the work... and all that may still be an uphill battle...
Maybe a solid grounded reason could be that the dealer bothched the rocker repair and Holden can't recomend any other dealer as being more competant. But you'd need an expert witness to testify that the first recall was botrched after he inspected the damage engine... Such experts are expensive and i'd suspect that may still not be enough...
Oh, and expect wanting to do extra work (like fitting a cam for example) while doing a warranty lifter repair is NOT a valid a reason for wanting to do the warranty work at some place other than a a dealer, simply because the dealer wont fit a cam at the same time...
One day, the law MAY catch up with the view that warranty work can be done at other than a deaeler network and at that time manufacturer process would be put in place to allow such. Even then, the process may preclude even non deealers from mixing warranty and non warranty repairs.
Until then, it's "warranty work through the dealer only" as also stated by Ron