Just had my A&O interview and absolutely bombed it. Oh dear
Very easy to self-criticise after an interview. I've had two ACs, one for a vac and one for a TC, where I was absolutely convinced I bombed it. I'd kick myself over things I'd said and micro-analyse my entire performance. Wasn't worth it- I ended up getting very positive feedback and told that I was close to receiving the offer. You'll probably also find that you performed better than you think.
If you're convinced you've bombed it, then I won't challenge that as only you can know that. However, your feedback will almost certainly be more positive than you think. "It's not a PFO until it's a PFO" applies at interview stage too.