Thank you all for the replies to this thread. Alas, it's all gone to pot. As of Monday my plan had been to get a train tomorrow (Saturday), to Stockholm, spend a couple of days there, then a train to Hamburg, night there to see friends, then train back to Amsterdam.
This morning I got a train back from Copenhagen. As I was approaching the Dutch border I got the message that the Danes are closing the border tomorrow at noon. Looks like I chose the right time to run away back to .NL.
I'm now back in .NL, and I'm expecting the rest of my interrail pass to be wasted unfortunately.
On the plus side, I do have lots of ideas for when we can travel again, maybe next spring...
J