I'm somewhat around your age and I've been through periods of anxiety and depression. For most part I've gotten over it. Since you're in the UK, the best thing to do would be to seek professional help.

For me personally, a lot of it had to do with me changing the way I viewed the world and things around me. Some things that triggered my anxiety were safety, how others around my age were doing so much better than me, how unfair the world seemed, stuff like that.

First of all what I did was I accepted the fact that I genuinely have no control over how most of the world around me. I can only control my actions and reactions to things. There's literally no point in worrying about the rest of the world. I also stopped watching movies and listening to music that was depressing. I only have so much time in the day, I don't want to spend it being miserable.

There's of course a lot more to it and it does take time but I hope it helped.