Good luck.
As someone who used to practice as a criminal solicitor, I might have some tips which could help:
Give yourself time to think as you talk. Ask for time to think.
Don't rush when you speak.Pauses are ok. People don't notice them - only you do.
Write a summary and just read it.
Read off notes you have written. Don't think you have to improvise. Don't think you have to remember everything in your head.
It's ok to take your time and look through your notes or check a report.
Make notes while someone is speaking. Concentrate totally on what they are saying. Highlight important bits. If you are asked if you have questions for them, and you do, say yes, but don't be afraid to say I need to check my notes. That is fine. This is important, you are not a lawyer (although lawyers do this all the time).
Likewise, if you are asking questions and you want to check something, just say I need to check something, I'd like to get this right so I don't waste time
Be professional and polite. Say hello and thank people. People can try their best and make mistakes because they lack knowledge and expertise - which is doubtless what you are going to Tribunal to get. Yes, we know they are lying toerags, but much better to be slightly disappointed or pitying in tone e.g. 'it is very hard for teachers with so many children in the class, you can't know them all'
It's ok to ask for help or time out or a loo break ('comfort break')
It's ok to pause and get a drink
Tell the Tribunal panel you are very nervous and ask them to bear with you - that is their job
Let your evidence do the talking
Good luck!!