Early supercurriculars for law/history/politics

Try contacting your local MP for a work experience, shadowing or volunteer work. Try the same with Citizen Bureau and maybe a local law firm in your region. Check the books advised by the unis on their websites, and start reading (try to complete at least 3 of them). Check intelligence squared for talks of people relevant to your fields. If you have any uni close to your home, check out their talks, workshops, etc. Sometimes they organise events open to the public (even at Oxford University).
Keep thinking on what made you decide for this course, because that is the connection that you will have to do when you write your ps. Also, make sure you write about yourself as a person and how these extra curricular experiences helped to improve some skills (which ones?) and if they made you see/feel/understand things differently after. This is an important connection to mention in your statement when you are listing the activities. At school, try to join a debate club or MUN. And maybe some leadership position as head of prefect. Also keep working hard to achieve the minimum grades of the unis that you want to apply - and preferably higher than those for predicted grade so you can beat the competition during the application process. I hope these ideas are helpful! Best of luck!

use future learn. it is so useful for online courses and gaining information and knowledge. it shows that you are interested and you have participated in wider reading/learning outside of your studies.