Hello,
My short answer is: study what interests you at the best university you can get into, do as well as you can, and then, if you have not done a Law degree, do the GDL.
My long answer follows.
I studied History at university and then did what was then known as the Diploma in Law, now called the GDL.
At that time, the course involved studying Constitutional and Administrative Law, Contract Law, Tort Law, Criminal Law, Equity and Trusts, and Land Law, and passing exams in each of those subjects after three terms of study.
After the Diploma, I did the old Bar course, for which as well as studying civil and criminal procedure, pleadings, and various other things, I also studied Tax Law and Company Law.
I then did pupillage in a chambers which went on to become one of the magic circle chambers (they weren't called that back then), and I was taken on as a member of those chambers.
I had planned to do a D Phil in History and become an academic historian, but I changed my mind at the end of my second year and decided to become a barrister. My historical studies and an interest in politics and justice inspired me to do this.
After a fairly busy time studying history, I found the workload for the Diploma to be light, and I found the law interesting (mostly) and easy to learn.
I found Land Law boring, but that may have been because the Land Law tutor had a boring teaching style. I also found Tax Law dull, but I had to do it because I hadn't done it at university.
I was taught Contract and Tort very well by a witty young barrister who, years later, I did cases against in Court (the current score is three one to me: sometimes the Padawan can out-fence the Master).
I paid little attention to Equity and Trusts until I got into practice, when I needed to use constructive trusts as remedies in commercial fraud cases. My Equity tutor, another witty barrister, became a drinking buddy but he wasn't a great teacher.
Constitutional and Administrative Law is interesting, and pretty easy for a History graduate. I already knew about the Constitution of the UK and how it got to be like it is (not all lawyers know this, but they really should). In practice, Public Law is easy and interesting.
While doing the Diploma, I read some jurisprudence in my spare time, because it's interesting.
Criminal Law is interesting as an academic subject but pretty horrible in practice, unless you do white collar fraud, murders, terrorism, and so on.
Do I wish I that had a Law degree? Sometimes. I sometimes skated on thin ice when I was a very junior barrister, because my legal knowledge base was a bit slender.
I wish that I'd studied Roman Law. It is foundational, even in the common law system (and much more so in the Civilian law countries). I have taught myself Roman Law recently because I am working on cases which involve jurisdictions where Roman-Dutch law is part of the legal system.
I do a lot of Conflicts of Laws because I have an international disputes practice. I have had to learn Conflicts on the hoof. It is interesting and quite difficult.
I picked up EU law in bits and bobs as I went along. Before Brexit, EU law came into about fifteen percent of the legal work of a general commercial lawyer who was not an EU specialist (doing Competition Law and so on). When Farage et al went on about EU law dominating English law I knew that they were lying, because 85% of the typical UK civil legal practice had zero EU content.
I am glad that I did a History degree. History remains my main intellectual interest, and informs my view of life. I still read History when I am not reading law books or novels.
My History degree was a great platform for becoming a lawyer. It taught me about evidence, and the presentation of a careful argument based on evidence.
I work at the pointy end of an adversarial legal system. My job is to annihilate my clients' enemies using words, and sometimes to make peace with them using words. The Oxford tutorial system helped me to become a good courtroom lawyer and negotiator, but I learned a lot about those things during my pupillage (with three barristers who are now big beasts of the legal forest), and on the job. Litigating is a lifetime thing, you keep on learning as you do it. No matter how good you get, there is always someone better than you.
Being a litigation lawyer is a great job. It's hard work, but it brings good rewards, and I don't just mean big sacks of money. Do I wish that I was a professional historian? A bit. But being a barrister ain't a bad second option.
TL/DR again: do what you think is interesting, whether Law or something else.