@Merton Kidd said:
As the developer/builder have long gone taking their profits with them, is it possible to sue the independent certifier engaged by them, especially if their is evidence that what was certified clear didn’t comply?

The certifier should have professional liability insurance – so they might be worth pursuing.  But it is possible that they did a “paper survey” – i.e. they made sure all the contractors had signed off on their work, possibly without even setting foot in the building.  The surveyors can then say they acted in good faith on the evidence that was available.  

That means you then have to pursue the contractors who will, in all likelihood, declare their firm insolvent within hours of receiving your lawyers’ letter only to reopen next day under under another, very similar, business name.

Getting back to the certifier – if you can prove they knew the work wasn’t compliant, then you’d have a case.  Talk to an experienced strata lawyer. Otherwise, you might be better off saving your money for the repairs.