Consider doing a summer school/course in what you're thinking of studying, or a hobby! Maybe start reading up on some things you find interesting relating to your A-level subjects (not content for the subjects themselves, just fun stuff) it'll help with writing your personal statement in yr12 summer term if you've already done the super-curricular things you put in the statement. A lot of people get to the yr12 summer and realise they've done almost nothing on the side, but by them they're too busy with a-levels to catch up on super-curriculars too. Make sure you do a whole bunch of relaxing though, a good break is needed before a-levels appear. Go clothes shopping if you're no longer wearing uniform where you're doing A-levels.
I did an EPQ (I got an A*), and it was good! It took me from October-September to finish it, so keep that in mind. You need to learn some research and citation skills so it's very handy for when you go to uni. Pick an interesting and out-of-the-box topic so you can use it for your uni applications and to make it fun.