I found this by GLP on his site (I hope he doesn't begrudge me for copying and pasting it here):
Q: What is generally meant by "English," "Scottish," and "Balkan" style?
A: The definitions of these terms seem somewhat fluid, apart from the fact that all tobaccos bearing these appellations contain Latakia. To my mind, it's more important to consider the difference between an English mixture and a Scottish one. In the first case, Latakia is a more dominant note, with Virginias and orientals filling in the gaps. A Scottish style blend, on the other hand, is dominated by matured virginias, possibly with small amounts of oriental leaf or a bit of Latakia for spice.
There's been some discussion of late about what a “Balkan Blend” is, and after some poking about in old ephemera - tobacconists' catalogues, old magazines and so on - I'm beginning to believe that the term is meaningless. Generally, people seem to apply it to an English mixture with a greater presence of oriental tobaccos, but this isn't really a fair cop. I suspect the term was probably originally used to describe a blend that is similar to the now venerated Balkan Sobranie. What's interesting is that this particular blend was dominated by virginias and Latakia, with only delicate sprinklings of oriental leaf, which is quite at odds with the current colloquial usage.
Probably better just to think of the two terms as being interchangeable, if we use them at all, since any definitions we create will be similarly aribtrary. For more on this subject, have a look at my article, What IS a Balkan Blend in Pipes Magazine