Hi,
I think it's completely natural to worry about exam results, it shows how much you care. I panic before my exams, and I know I'm not alone in that, it's stressful to think of all your hard work coming down to a couple of hours in a hall. What I can say is that it's never as bad as you think it'll be. Even if I leave the exam hall convinced I've failed, I never have. The fact that you're predicted A's is proof that your teachers believe you can do it.
Also, universities do tend to take a more holistic approach, so even if you don't acheive the exact grades you're hoping for - which I'm sure you will - there are many other factors, such as your personal statement, reference and interview (if you do one) that they will consider.
Best of luck! Please don't hesitate to reach out if you have any more concerns.
Safi
2nd year Linguistics