Having just come back from touring Italy, I think I can say that anything south of the olive line (that is oil producing regions) would constitute Southern Europe. This, typically like European countries is not as useful as it seems as France, Italy etc. all exist both above and below the line, but there is definitely a cultural (and ethnic) difference between those living in colder and warmer climates.

Similarly I'd suggest the point at which grape production for wine tails off would signify the start of Northern Europe. Wine grapes are grown in England, but I wouldn't call England a big wine producing country. Similarly, the Netherlands has some wine production but I wouldn't class them as a major wine producer and as such part of Northern Europe. North of Dusseldorf or Hannover? Arguably Northern Europe. South of Dresden? Probably Central Europe.

I completely appreciate this is made on no scientific basis whatsoever and I'm probably completely wrong, but if you visit Spain, southern France, Italy, Greece and Western Turkey you'll see remarkable cultural and ethnic differences and similarities between them and Austria, Poland, central and southern Germany and in turn Northern Germany, the Netherlands, northern France and the UK.

TL;DR - Europe's a mess. We can't even really all agree on what it is.