I turned my cd set into dvds this way using jigdo, so it stands to reason it should work the other way around
If you havent used it before, it is pretty easy to install and use, i am fairly sure its in the debian repositories. Anyway, once installed, you need to download the .jigdo file for the cd(s) that you need and the appropriate template files.
Stable ones found
here.
Go through the motions and once you reach the "Files to Scan" prompt, tell jigdo where to find your dvd and it will nick all the files it needs off the dvd and you will be left with cd iso.
I should warn you that there may be a few files (not too many i hope, but i cant be sure) that are different on the CD so you may end up downloading them but jigdo will do that for you if you enter a correct debian mirror.
http://www.debian.org/CD/jigdo-cd/ will tell you the best one.