It's easy to say be calm, relax, don't worry etc.
The reality is that you are going to worry, and you've probably been worrying for some time leading up to your test.
The other reality is this:
What's the worst that can happen?
You will NOT be fined, tortured, imprisioned, prosecuted, killed etc. or otherwise come to any harm.
The worst thing that can happen is that you fail and have to re-apply and sit the test again.
I am not taking this lightly and I understand the duress under which you find yourself, so;
good luck, mate; ENJOY the drive; the examiner is not the enemy.
Kindest regards,
Paul.