Those of you who are planning to get ahead on your A-levels because they're such hard work are going to be wasting your time. Yes, they are harder than GCSEs, but a) your teachers will appreciate that so you'll be learning a lot more in class, b) you'll only be doing 4 or 5 subjects so that offsets the extra work, and c) if you don't relax at some point you definitely WILL lose concentration at a later stage. And this comes from someone who's just about to sit A2 exams. Enjoy the summer, make the most of the time you have, and do the kind of thing you never would otherwise have time to do (write a book, make a film, go on a long trip somewhere, etc). If your idea of fun is sat inside with textbooks, then so be it, but trust me you'll be wasting your time.
Personally my plans for the summer are a break away with my mates at the start of July, a two-week trip to the Dominican Republic to do charity work with my Scout group, maybe get a job, do a bit of reading in preparation for my law degree (unlike A-levels, degrees DO require you to read ahead - it's pretty much mandatory) and then fill the spare time with guitar, football, sleeping, and whatever else takes my fancy.