law and criminologyWatch
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Not exactly sure what you mean by ''can we study any course you want to?''.
In any event, Law and Criminology (at least at my Uni) was essentially 2/3 Law and 1/3 Criminology. The people I knew on the course generally did better in their Criminology exams/coursework than they did in their Law ones, therefore suggesting that Criminology was easier than Law.
Have a think about what courses you would be able to do in relation to your results, where you see yourself after Uni and what you want to get out of your degree. E.g. I did my Law degree because I wanted to qualify as a Solicitor as soon as possible as opposed to picking it because it was the most interesting/fun. You may not have the aspirations to be a Solicitor and therefore you may want to do Criminology on its own rather than have to do elements of the Law degree too.