NCAT doesn’t automatically allow parties to be represented at the tribunal by a solicitor or barrister. As mentioned above leave needs to be sought and is intended to make NCAT hearings more accessible especially those without a lot of money.
In my limited experience parties seem to “try it on” with using solicitors first and only represent themselves if there is pushback. Tribunal members may even prefer a solicitor as the matter will most likely be presented with much better clarity and with only the relevant points raised than the average owner with a bee in their bonnet.