I think this is really tricky. I used to do informal sex ed, not in England, when I was studying.
The person who ran it was quite 'forward thinking'.
It was for 15 year olds and focused on relationships. In most schools, this all went down quite well. It was workshop based, lots of interesting discussion.
I remember one school I went to, it had a more formal vibe, the students were much more, bookish and academic.
They could not have been less interested! I sensed they were slightly horrified by some of the things we talked about.
I left feeling, bad, like I'd pushed something on them that they didn't want to hear, or taken away some kind of innocence.
At the same time, maybe it might come in useful, maybe some of them did find it helpful, but just didn't know how to or didn't like talking about it to adults.
So I'd probably say something like it was good that you engaged with the discussion and good that you had your own opinion about what you talked about.
I suppose in a way, ha, part of the point of the sex ed, was also to encourage the kids to open up and talk to and discuss with parents, because far better that they have a relationship where they feel they can have a chat about anything to do with sex if they wanted to. So maybe just go with the flow on it.