Hey, I can kinda relate. I lost almost all of my friends at one point and felt like I was left with no one. I would often watch my ex best friends laughing together at lunch as I sat alone, I would often sit with them only to be ignored but I just didn't want to be alone. You get pretty good at being comfortable by yourself, but I still felt so lonely all the time and I preferred being in lessons and would often stay in my classrooms throughout break.
If there's nice people in your classes, try hanging out with them. I know that's easier said than done - I often thought about joining a class friend of mine's friend group, but the issue was the rest of their friends weren't so nice so I never did. I did, however, end up becoming good friends again with an old friend of mine who I had stopped talking to for a while - I'm still great friends with them now. (however, as you said, they had their own friend group so I didn't see them as often as I'd have liked)
It's good that you have the start of the year to start integrating yourself into a new group. And old friend of mine joined my old friendship group at the start of year 11 because she shared a class with another of my old friends, and we were more than happy for her to be a part of the group! But only because she put herself out there and started talking to us and hanging out with us, otherwise we'd've never known her.
Do you have friends outside of school? Especially as you grow older, you'll start to gain friends outside of school from different things you do. Also, once you leave school it's like everyone almost instantaneously forgets about cliches and groups, and you realise how unimportant it all was and the fact that there were so many nice people I could have been friends with if only I'd had the courage to try and talk to them and hang out with them.