Do I need Law A Level to study Law at University?

Not at all! It can be a good starting point for some Law students, because some exam boards at A Level teach you the core modules covered at University in a very similar depth e.g with similar cases, everything sounds familiar. But, everything taught in a Law degree is taught assuming no one knows anything so you wouldn't miss out on not doing Law at A-Level. It is useful to have it however, because it's very similar to the degree and will help you decide if you really want to study it!