Since you are in 6th form now and there are new people, you can branch out and try meeting and getting along with the new folk. For me, I continued at the 6th form at my school and it seems people are sticking to their own groups as about 1/3 people are new. Back when I was in school I stopped hanging out with a group of friends for various reasons and I had no one else to hang out with for about two years except my sister and her friends as everyone already had their own groups, but partly because I was fed up with the whole friendship group thing so now I'm happy for this chance to make some new friends. So good luck!