Hi Shaun!
I think if you're planning to study in the UK, that would probably be the best way to get over here if you're dead serious about moving here. You would obviously have to find a British university that offers your intended major, and apply as an international student via UCAS.
To be honest though, American high school really isn't enough preparation for heading straight into a British university. The educational systems are very different and the students around you might be a little older and more advanced in the field of study than you are because they'd probably actually started studying it in college before they got there. (You actually start focusing on your major in the very first year of uni, and that can be intense if you're straight out of high school. Plus, if for whatever reason you want to change majors, it's a huge hassle.)
I'm not saying it's totally impossible to go right into a British uni, but it can be especially challenging because on top of all the coursework, you also have the stresses of adjusting to a whole new country alone, which takes up a severe amount of energy.
I really would recommend a year abroad or something along those lines first, because you can't be sure until you're already here that studying and living in the UK is what you really want. It's a huge commitment. But if moving to the UK really is your dream, by all means go for it.