I am so pleased that you posted this as a full question! The online chats are absolutely great for covering lots of topics, but there is so much going on that it is difficult to explain things in full. And your questions about geophysics, not just this particular one, really need more than just a few quick sentences.
Geophysics is perhaps the most beautiful of all the sciences. It is the study of the earth as a body in the solar system, almost as if we were studying another planet, with its atmosphere, structure, history and dynamics. However, this planet is special. It is our own. It is home. And it is the only one we have. Additionally, it is the most beautiful planet of all, with its mountains and oceans, volcanoes and aurorae, tranquillity and storms, . Yes, the way I think of it, it is like doing hands-on planetary science. However, unlike the other planets, which are so difficult to get to, our own is right here and we can study it up close.
It is an important science, not just from a purely scientific knowledge point of view, but also in so many practical ways, from land management, to mineral exploration. It is also used for things like energy, such as hydro-power or offshore wind farms. It is also used by other branches of research, such as seismology, geodesy or climatology. Some geophysicists even use their expertise to go on to study other planets. There is a lot of work for geophysicists to do!
The first advice I would give, is to look into the different aspects of the subject. See what it is that interests you. Perhaps studying volcanoes or earthquakes is appealing. Or maybe you are interested in the extreme upper atmosphere on the edge of space. But by starting to investigate the subject as a whole, you will start to appreciate the different areas of this wide field. This will help you understand websites and other information when you are looking for courses and universities to study at.
next, you should think about your school subjects and make sure you work hard on the important ones. Chances are that if you are attracted to geophysics, you’ll also already like some necessary subjects like science. But, like almost all sciences, you will need mathematics too.
A good thing to do is to is to check with universities too. It may sounds a bit daring, but try getting in touch with the geophysics departments. Seriously, put “geophysics university UK” (or something similar) and track down the universities that offer courses. Send them an e-mail, explain you are a student, who is interested and would like to know more. You may be able to get work experience this way (which is another good tip!) or even a summer job. You will also then be starting to work out where the interesting courses are… something that is important for later, when you need to decided where to apply. Some might not respond, so make sure you send e-mails to more than one place. But if you are keen, then the universities will actually be interested in getting your attention, as they are always out to find the best and keenest students!
More generally, there is the European Geosciences Union (http://www.egu.eu). I have written to their education officer to find out what advice they can offer (and will let you know when I hear back from them).
Of course, this week you have a fantastic opportunity to ask as many questions as you can. However, from the intelligent comments and queries you made during the online chat session earlier today, I have every confidence in your ability to succeed.