Here's an update!
In the end I decided to reinstall minime 2009.1 on that partition and, as it doesn't have any printing applications included, they had to be added. These are later versions than the original that worked, and I had the same problem: the printing gets to the printer queue and just stops. However, I can now cancel, and as before the escputil routine tells me the ink levels.
I can, however, print the same file from the same installation on my Brother HL-20 downstairs via the network, and that prints OK. (It was clever enough to discover that remote option all by itself!)
I then thought that maybe there was something missing in minime that I hadn't added, so tried the full 2009.2; that worked initially, but not after I had updated, and still failed when I converted it to KDE4.
So it seems there is a bug somewhere in the Epson driver.
But, oddly, the one working installation that will print to the NX200 is my test KDE4 one and it has exactly the same versions of printerdrake and gutenprint as the one that fails. However, that has other faults, mostly due to my experimentation while I was trying out how KDE4 worked, and isn't fully working to my liking. (Wine doesn't work for example.)
The only truly stable installation I have is the trusty old 2007, but that was too early to have the NX200 drivers. (My love-hate relationship is rather on the latter side at present!)