You can always expand on your existing hobbies, twist them torward the right targets. Like baking for example - that's pretty creative. You talk about how it relaxes you: something that gets your mind off academics and gives your an outlet. That ticks the 'has an outlet and therefore won't lose it halfway through their third year' box.
Likewise, music is always good for pretty much the same reasons, as is jogging. Talking about your emotional response to music and books is a good way of telling them you're not some kind of academic robot with the empathetic understanding of a turnip.
If you want a good book to read, check out AJ Cronin's 'The Citadel' - it was pretty important in the formation of the NHS and is fiction, which is great because:
a) It's not a complete snooze-fest.
and b) If you talk about it in a medical interview, the panel won't pounce and start asking you about the terrifying specifics of liver function because it turned out one of them wrote it and the other two edited.
Just a couple of tips there - it sounds like you've got plenty to keep you going. Just inflate it. Good luck
But yes, I do have interests, like the clarinet and I also read and jog and go to the cinema and bake...but I'm just unsure how to talk about them... because baking a cake that tastes like a malteser isn't really a major achievement 
First Year in Bristol! 
