Hi Basso,
Although the majority of my classes are face to face, I also do online classes. My students and I generally find that the classes are still effective, however they aren't quite as efficient. What I mean by this, is that you can go through the math material faster when you have someone right next to you who can correct you. With that said, I use an online whiteboard that allows both of us to write on the same screen, and skype so that we can see each other. This would allow us to go through all of the the material as usual, but takes about 70 minutes to go through what would normally take about 60 minutes.

Thus, if you have no decent private tutors available in your region you're probably better off finding someone online who really knows the exam since the knowledge that you need can still be transmitted effectively, but perhaps not quite as efficiently.

I've also heard recently that the economist online program is not so bad so if you don't want to go with a private tutor maybe you should check it out.

Cheers!
Dan