Hi! I am in Year 13 now and I received an offer for Linguistics at Cambridge, so something slightly different, but I can tell you about my experience.
I am particularly interested in the history of English and in how languages develop, so I got my hands on some books on Old English. I quickly realised that most of the resources we have to learn about Old English are poems, so after doing some more reading I came up with a short introduction to the Old English language, and gave a presentation on the art of Old English poetry to my school's poetry club, complete with a crash course in Beowulf. This was one of the things which I wrote about in my statement.
I will say that it's definitely not enough to just have done the things - you have to have interesting insights about them. In my statement I did talk about the experience of researching and presenting, demonstrating that I had a real passion for the subject, but I spent more time discussing observations on the Old English language that I gained from the experience. I talked about the phonology of Old English, how it was similar or different to Modern English, and then linked this to other research that I had done during my EPQ. In this way, I was able to take an experience that I had had and elevate it into something unique by showing that I was thinking about the language in a more in-depth and complex way, and that I was able to draw links between different areas of linguistics.
I hope that this is helps, even though I'm not studying the same subject!
Good luck with your applications!