As a postscript to my ripping (get it?) yarn. I ended up using SmartRipper to grab the vobs and decode the AC3 out of them.

Because I didn't want to do anything with the video I ended up using beSweet with the VOB input DLL to convert the AC3 to a WAV which I then cut up in Cool Edit Pro 2 and then nogapped in lame. Lovely stuff!

Now I have to transcode my new Depeche Mode DVD but thats got an LPCM soundtrack, back to square one? Possibly...