Hi. I'm in S5 (equivalent of Year 12 in Scotland), and I also want to apply to uni for English Literature, so I'll share some of what I've been doing.
I've been trying to read a wide range of literature, from plenty of time periods and genres to getting in more plays and poetry. From what I've heard and from some of my own research, lots of English applicants nearly exclusively mention novels in their personal statements. By showing admissions tutors that you engage with multiple forms of literature, you can help yourself stand out. You could also do this by comparing reading a play to how it is performed on stage, or from comparing a piece of literature with its film adaptations or retellings.
Additionally, I've been reading books about literature. One that I've found really useful was 'Much Ado About Numbers' by Rob Eastaway. It was a bit waffly at times (which I always hate to say as I've met the author and he's absolutely lovely), but the book's general point that there can be many (often unconsidered) influences on a writer's work is something that was interesting to explore. I'm sure there are plenty of other books out there that explain this in a bit of a better way, however.
Having a bit of a theme for your personal statement is good. E.g., "I read Eastaway's 'Much Ado About Numbers' and I learnt .... This lead me to read .... ect" Obviously, that's simplified, but having one activity lead on to another is something that you will ideally need to do in your personal statement.
One thing that really helped me when trying to figure out what supercurriculars I should do was looking into how to write a personal statement and making a 'plan' based on what I had already done. This let me see what I still had to do, allowing me to be more focused in my supercurriculars instead of doing everything under the sun.
When people say "quality over quantity" for supercurriculars, I find that that's not very helpful in understanding how much you should do. Think about it in the sense that you'll want around 4 paragraphs (it can be a bit less or a bit more, depending on what you want to say) about English across questions 1 and 2. Within each of these paragraphs, you're going to want to link/show progression between at least 2 activities, however I have seen some advice saying that 3 linked activities per paragraph is optimal.
I hope this helps, and if you have any more questions, feel free to ask me. 😊