The key to the EU single market and the EU in general is making SMEs and people feel at home in "it". Has not happened yet.
And I do not mean just trade of goods or freedom of capital movement.
The Euro was/is an element of a single market and a single "space", not a goal in itself or the tool for bankers and central bankers (and speculators) it became. After all is said and done German/BuBa and their European disciples' philosophy undermined the Euro via the inflation obsessed policy allowed and its impact on the Euro exchange rate and hence its trade balance with the rest of the world. The EU/Euroland is inter alia a victim of China exports more than the US and a more "fortress Europe" Eu or Euroland will not happen (for better or worse) because certain European interests will not allow it.