No reply from potential supervisor of my dreams: is it OK to try meeting them in person?
Some important things to know:

1) Many professors receive dozens of unsolicited emails a day from potential graduate students, and essentially ignore them because they can't keep up (although having a form letter "no more students!" response is, perhaps, a nicer thing to do).

2) Many (most) faculty don't admit students without having some idea of how they will fund them, so it's not unlikely that this specific researcher can't really offer you a spot in the department. 

3) In my experience, most of the unsolicited emails are also way off the mark in terms of research topics, so the most important part of your communication with this researcher is conveying that you a) actually know what they do, b) have something useful to offer, and c) that you are applying to the department and would like to work with them. And it's fine to ask to speak with them briefly (by email or phone) about whether you would fit in with their research plans.  They might ignore you.

If you are actually in the area and want to set up a meeting (by email), that's one thing, but I don't think you should fly to their country and ambush them. 

Not to be a downer, but just because you think this person is the perfect advisor doesn't mean that you are their perfect student (or that they want another student right now).  That said, you can still send a nice follow-up email and apply.  You might want to apply to some other places too, however.