Sedation During Surgery?

I've just had my final meeting with my surgeon before my Phakic ICL early April. I've been very happy with all my consultations etc and I'm comfortable with the surgeon.

However, it was brought up today that I should either pay for sedation (they want £300 for?!) or get some diazepam from my doctor.... This is the first I've heard about needing sedation? Everything is numbed anyway so why would I need it? Am I missing something?

Honestly ngl it's made me more nervous about the op with this being brought up! Any advice would be super welcome! Thanks!