Well, no. With a predicted AAB you have a very good bracket of potential universities to choose from. Why choose to quit and restart due to one bad mock and being behind on work?
There are tens of thousands of other students right now who are in the same situation as you but know that they simply need to work harder and try as hard as they can. If unfortunately you don't do well in your final exams, then restart. Being predicted 2 A's and a B shows you have great potential and clearly intelligent.
Try to push past the set backs, get back on track for coursework and see how your next set mocks go. Don't through in the towel after one bad test.