You made a good choice by choosing to study the subjects which you did well in at GCSE, as when looking at your GCSEs they will care more about what you got in your most relevant subjects. However you said you are targeted ABB, however you will need to get AAA at AS to be competitive AND will need to be predicted at least A*AA. It's not impossible, I know of people who have gotten into Cambridge (and Oxford, believe it or not) who have gotten in with 3 or less A*s, and even no A*s. It's not about being good at everything, it's about being amazing in the specific subject you want to study.
Saying that, you want to apply to Law. With these kind of competitive courses like Law and Medicine, being good at everything is kind of important, whereas in something like Physics they would only care about how good you are at physics and maths. Therefore I'm not sure you would be a strong applicant. Are you sure you want to do Law? Have you considered other courses based on your A-Level subjects e.g. History, English, Philosophy, or Theology? Law has 5 apps per place while Theology only has 2 and History has only 3.