Don't do spanish if you're native. Universities will frown upon, judging it as an easy option, where as if you take something else they will see native spanish as a great bonus. I'd take two sciences with Eng lit and history, possibly taking the EPQ if you get the chance. That will give you both specialism to go into whatever science/ english/history degree you may decide you want to do, or alternatively demonstrate a range of skills that are perhaps transferable to something you haven't thought about, or had the opportunity to study yet. Also, all of these subjects would be very highly respected, giving you a good shot at a top uni place. Besides, you'd probably be bored to death studying a language you're fluent in.