You are, presumably, a school student at the moment? If you are interested in the law, as a subject, then take the standard LLB and not a "Law plus something else" degree. It would be completely unrealistic for you to know which field of the law you want to go into at this stage - so don't worry on that front.
As I've mentioned on other threads, the profession is incredibly competitive to enter. I have no idea what A-Level grades you're aiming for (or have already received) or which Universities are on your radar. But do you have a clear understanding of the various paths into the law, the types of work that solicitors and barristers do and, most importantly, how hard it can be? On a previous thread, a poster was explaining the difficulties they faced and how they had wished they had known more about the challenges before they followed this route.