Well, you should keep in mind that language is a major issue for ATC. For example, in France most of ATC is in French, with the pilot leading the language choice.
So you can have an AirFrance "trois cent neuf" [309 - read as: three hundred nine] and a Speedbird three-zero-nine which could get confused specially with cockpit noise. Add the various accents and you can have a mess. On top of it, France, Italy, Spain, Portugal and some countries in Eastern Europe as well as Russia operate in their languages with very little english knowledge and see how confusing it gets. See below for details:
In Canada, a French speaking quebec pilot may choose French, but numbers are read each number at a time with French use apporaching direct English translation (listen to the CYUL feed). This is why most French flights use English in Canada while Quebecers use French!!
In France. numbers are read as per usual French use (thousands are read as three thousands forty three in case of a flight number 3043). And most of it is in French. And their english accent is not the best; after all English is not their language.
In Italy, most of it is in Italian and the english accent is not exactly top of the line (this depends on the controller's knowledge).
In Spain it is the same. Portugal as well.
In Eastern Europe, they are slowlly switching to English (Lithuania, Latvia, Czech, Slovakia, Hungary, Poland, Estonia) but not in Byeloruse or Russia where altitudes are given in meters and Russian is prevailing. Altitudes are read as "climb to altitude 7 thousands eight hundred" for example, in heavily Russian accented english. You can feel the change because as the flight approaches the border area, the plane either rises or descents to follow meter altitudes (in flight, whether it is meters or feet or fingers makes no difference since it expresses separation space but maybe Russia doesn't agree with this explanation).
Greece is mostly in English (good for holiday listening). In the Balkan states, since most of their flights are overflights, are all in English.
Morocco and Algeria flights are all in English even though their languages are French and Arabic, and use English even when they fly over France (don't know why).
All of Scandinavia is in English and so is Belgium, The Netherlands and Luxembourg. Switzerland is in English too but take a listen to the Geneva feeds to see some exceptions for flights coming from France.
Hope this helps. Try and listen to the European feeds and you will see.