http://www.ddcts.com/aboutus.htm

Dandong Chosun Tour Service. This is the Dandong-based agent I was trying to find that some European passport holders have recently been able to use to get into North Korea by train. Usually as part of a Chinese group, but once over the border, an English speaking guide is provided for the non-Chinese. I'd heard an all-inclusive 4-day trip is about Euro 500. Not sure about longer trips nor if passport holders from non-EU countries can participate.