Work before Year 12Watch
You can do a lot for your personal statement - you can read some books, newspapers, academic articles/ journals, do some essay comps, research project, prepare for EPQ, watch lectures, youtube videos, documentaries, listen to podcast, do some virtual work experience. Tbh I would suggest writing down some things to do in year 12 as well so you dont miss out on those - for me, I would write down some summer schools I wanted to apply to so I dont forget. Doing these things wont boost your personal statement - it's more for your interest and engagement, which is really important for a personal statement. What will boost your personal statement is how you use the things you have done effectively and making it personal to you, which will make you different from the generic statements. Tbh some universities don't look at the personal statement for medicine so wider engaging will help you for the interview when they ask you questions from their list.