Actually I'd try to represent the "blocs" in the EU:
UK represents UK, Ireland and Malta
France represents France and Belgium
Germany represents Germany, Austria, Netherlands, Luxemburg and Slowenia
South represents Spain, Italy, Portugal, Greece and Cyprus
North represents Denmark, Sweden, Finland
East represents Estland, Lettland, Lithuania, Poland, Slowakia, Czech Rep, Hungary, Bulgaria and Romania
This way you'd have the economic and cultural zones bundled up a bit.
France and Germany should have very very strong relations, followed by very close relations towards UK, South and North. East should have only strong relations ... with a few Kashinsky events thrown in.
If you want to break it up even more, make Spain/Portugal, Italy and Greece/Cyprus separate nations, and you might also separate the East into three blocs (baltics, eastern and balkan). Scandinavia is culturally and political very close, and shouldn't be broken up at all.
Basically I'd go with either 6 or up to 10 "nations". Max would be:
British Islands: UK, Ireland, Malta
France: France, Belgium
Germany: Germany, Netherlands, Austria, SLovenia
Iberia: Spain, Portugal
Italy: Italy
Greece: Greece, Cyprus
Scandinavia: Denmark, Sweden, Finland
Baltic States: Estland, Lettland, Lithuania
Eastern Europe: Poland, Slowakia, Czech Rep, Hungary
Balkan: Bulgaria, Romania
Hungary should be placed with Poland and Czech Rep for economic reasons. Same about Slovenia and Germany (in reality Austria). Greece and Romania/Bulgaria don't have much common ground either, so don't stack them into "Balkan" together.
About the other states of former Yugoslavia (plus Albania), they should stay separate "minors" as should Turkey ... actually its more likely that the whole Balkan AND Ukraine will become EU members before Turkey I suppose.
If you go along the "central EU plus surrounding civs" version ... make the 6 founder nations as core EU: Germany, France, Italy, Netherlands, Belgium and Luxemburg.