The economics of most chocolate making are that for most chocolate makers, it’s not worth setting up a separate production line for milk chocolate and for dark. So most dark chocolate is made with machines that have also been used to refine milk chocolate. Even if they are cleaned down thoroughly after use, the chocolate maker still can’t afford to take a risk and has to label their chocolate as ‘may contain traces of milk …’ etc.
The new trend for growing country chocolate may help you though. Most of these producers would have to import milk powder from consumer countries to pass US and European food laws, so its not really worth their while to make milk chocolate at all. Therefore many of these factories are completely dairy free.
This could help you out, as some of them now have couverture available in Europe. Grenada Chocolate Company couverture can now be bought from HB Ingredients (www.hbingredients.co.uk) and Pacari from Ecuador now have retail bars here, and couverture available from Holland.
I hope that helps a little!