You have received a number of helpful wake-up calls but I will just add a few things:
1. You may find that a law degree allows you to study areas of law where the law is actively being developed to help people in difficult or disadvantaged situations. Modules such as family law, mental health law, equalities law, as well as theoretical choices such as law and gender, law and war, are increasingly taught at universities. So do take a moment to identify the courses you are interested in as you may discover that they have offerings that interest you beyond the usual 'core' subjects.
2. It is very straightforward to pass the BPTC/LPC. Both have fairly high pass rates and they are not demanding if studied full-time with no other commitments such as raising kids or working part-time. If you struggle to pass them, you are likely not cut out for the profession (indeed, those who struggle to pass all of the modules on their first attempt will usually struggle to secure a training contract or pupillage). But it is a bit early to be thinking about these issues right now given that these exams only become relevant if you wish to enter legal practice.
3. If you would like to find out more about the law degree, you should find the kind of law materials that are studied by law students and read them. It's not that difficult, and there are no good substitutes to that. Some universities put up introductory reading online so that may be a good place to start if you don't know anyone. Make sure that you are aware that you will need to study 'dry' areas like land law and contract and that you will need to have the ability to push on through difficult and boring material in time pressured conditions. If you don't think that you have that kind of resilience, that's already a bad sign.
4. Keep in mind that you do not need to work as a lawyer to help justice be served (you can work as a police officer, or social worker, or trade union officer, or something like that). Also keep in mind that the areas within law that deal with sensitive issues like 'justice' are probably a minority and do not pay well. You may end up in a situation where you never make enough to pay off your student debt even after 30 or 40 years.