I wore a trouser suit to my interview - it's better to look too smart, than not smart enough. Make the other candidates question their outfit, but most importantly - feel confident.
I had a 15 min teaching episode, a subject audit, practice numeracy and literacy test and the interview and was offered a full place the same day.
They're expecting you to be nervous and take that into consideration (it's a life-changing step into your career, they realise this).
The worst part will be your presentation, take a deep breath, practice it a few times with family/friends/partner and when you get in there it'll all come out. If you mess up, just correct yourself and carry on.
As for the interview, you should already know why you want to teach primary. I was asked what qualities teachers had, my proudest moment in life, what I do outside of school, evidence of working in a team and something in my subject that inspires me, but they may ask you about things that are happening in education atm (attainment levels are changing etc), or for your experience.
Chill, you got this.