Applying for a graduate course not related to my previous research experience
I'd say, go for it! Two reasons:
1) If you stay in academia, you're going to use your creative and imaginative skills a lot. And my experience is that they don't work much if you aren't interested in what you're doing.
2) You will have an interesting edge over other candidates since you come from a close, but not overlapping area.
It will take determination to enter a new area, but I think you're absolutely on the right track in pursuing what you're passionate about; and yes, you're still in time! Don't give up. :)