Ersa: even after Brexit the CAA wouldn't issue exemptions, that would grow out of their control very quick due to every one asking for exemptions and after granting one person, they can't deny another person.
(after Brexit, we still have to obey EASA rules, that won't change. We're still in Europe, just not in the European Union (just like Iceland, Switzerland, Liechtenstein and Norway)).
But on topic again: A 3 year period should be long enough to pass a CPL course.
Bad coaching of the ATO unless you left everything last minute and to make it worse, last minute during the winter period....(probably 50% of the lessons get cancelled).
The ATO and/or examiner should have checked that your CPL exams expired on the postponed test day and there was no point doing the test since at that point you didn't have any valid CPL ground exams so regardless of the outcome, you wouldn't get your CPL license.
Even if on the test day the exams would be valid it wouldn't work, the exams need to be valid when the CAA is issuing the license, so not just valid on the test day or when you send off your papers, but always add 30 days for the CAA to process the application. If it takes them longer than 30 days, then you can appeal but otherwise not really.
There is no other outcome then to resit the exams again.
The only thing you could ask for, is a refund for the test from the ATO since they shouldn't have tested you.