As has been said above there are 'failure items' and there is an overall standard of performance - both factors need to combine to pass a skills test.
or should I take it on the chin, learn from the other genuine mistakes I made during the test and do better next time?
indicates to me that it was not just a single error.
If there is a conflict of procedure between what you have been taught ( and subsequently flew ) and what the examiner thought you should have done then I would ask for clarification.
BUT do discuss it with your instructor / CFI before doing so!
HWB