I heard that the EPQ (not only from my careers adviser, but from others) is a great way to be independent in your research and study which apparently universities love.
I've put myself down for it next year and am looking to study Medicine, so my careers adviser recommended doing something based around Science for this. A guy from my school got an unconditional offer from one of the Oxbridge universities, and he also done the EPQ and said it was great to talk about in his interview