Extra curriculars have no bearing on your application. They are great things to do for your personal enrichment and may teach you transferable skills which could make you perform better academically too, but no Oxford tutor will care whether you have been on school council, play the cello (unless you are applying for music) or have a DoE gold.
People on here talk about super curriculars (ie learning about your subject beyond the classroom) a lot as though they are some kind of checklist with you needing to have a certain number or they have to be of a certain type. They don’t. It is not about what you do, it’s about how you reflect on that and integrate it into your understanding of the subject. Again, it’s all about how well you translate those experiences to show genuine motivation for the subject and an ability to learn and reflect. Reading a couple of books and talking about them interestingly is just as valuable as winning an essay competition or going on an expensive summer school.