I had exactly the same thing when I started my course. I was really nervous, didn't know anyone, and I'm quite shy. I was one of three mature students and the other two were already friends. All the other students were a LOT younger than me.
But as has been said, once you start doing treatments on each other, you get chatting and before you know it, you're friends! Just try to work with as many different people as you can, you'll soon settle in.
With the assessments, your tutor is not going to make you do an assessment before you are ready for it. As long as you know what you're doing and why you're doing it, there probably won't be any question you won't be able to answer. They're not going to ask you things you haven't covered.
I really enjoyed doing my course. Yes, it's a massive learning curve, but if you really want to do it, then just go for it. Throw yourself into it and you'll never look back.
Just a little extra point - At a salon I used to work at, we had a work experience girl from a local college. Her waxing was absolutely dreadful (bearing in mind that she'd passed her assessment!), and she told us that because she didn't like waxing, she used to try and avoid it if she could. So we had to explain to her that waxing is a basic beauty treatment and if you can't wax, NO-ONE is going to give you a job in a salon. My point is, if there's a treatment you find difficult, get as much practice in it as you possibly can. Get the equipment to do it at home and just grab everyone and make them have that treatment! You're not going to get this opportunity again, so make the most of it!
Most of all, HAVE FUN!!!!!