Building my university application to study law

I’m currently in year 12 and I am aiming to get into a good university to study law.

For context, I currency am looking into Warwick University and have dreamed of going there for years. I would love to go to Oxford but I’m not sure if it’s too late since my GCSEs are over and I didn’t get outstanding grades (my brother graduated from Oxford but he achieved mostly 9s in his GCSEs). I got two 6s, three 7s, one 8, and one 9. I am aiming for top alevel results but Im not sure this would be enough.

I’m currently looking into things I can do outside of my academics that can help build my application but since I live in a small town without many opportunities, I’m struggling.
I would take any advice. I’ve seen many talk about essay competitions on here and I will look into those at the start of next year.
I have been trying to find places to volunteer, or find online seminars to attend but have been unsuccessful.

Please could someone give me some advice on what I can do