If your predicted grades are below the threshold and you don’t have any mitigating circumstances/meet widening participation criteria, your application will probably be sifted out immediately. It’s brutal, but it’s the way of it. Saying that, most schools are willing to be flexible with their predictions should pupils need them to be for uni applications, so it might be worth having a chat with your subject/careers teachers to see if there’s any leeway.
The one thing I’ll say though, is that A levels only get harder in the second year. So if you put a lot of time and effort into these mocks and have come out with (very respectable, I promise) ABB as your grades, how realistic is it that you’ll meet an A*A*A offer? If you know you couldn’t have done anything more for these exams, it might be better to set your sights on schools with grades more in line with the results you’ve produced. At the end of the day, UCAS choices are entirely personal to you, but I would advise that you think very carefully about what kept you from getting A*A*A in these exams before making any decisions about whether Cambridge is a good idea or not. But like I said, if you do draw the conclusion that there were circumstances that you would better control in future exams that caused the problem then go and speak to your school and see if they’re willing to bump your predicted grades to A*A*A.