Indeed, Physics is interesting.
I must warn you, though, that Physics is entirely a matter of understanding the subject as opposed to memorising facts. Think of Physics as a 2nd Mathematics, only this time you have physical matter to work with. More often than not in the exam you'll be given circumstances you've never come across before and you're expected to apply mathematical knowledge and educated assumptions in order to reach an answer. But it is VERY rewarding.
Maths, to take alongside it, is a must. You'll be at an advantage with Further Mathematics, and with economics, because you're bound to take Statistics in either of those, and Physics does have a statistical quality to it.
It's very fun! And should you find yourself engrossed in the subject, don't worry about going off to research things that aren't in your spec. I'm on OCR A and I've written a research paper on Quantum Chaos, which I don't think is covered until one of the later years in university.
It's a magical way of expressing mathematics and forming logical reasoning within your head, as well as being one of the most respected A-levels out there.