Yes, I only allow wifi downloads, so the fact that it stopped downloading when I left the house was expected behaviour.
I have tried using the download option in the menu, however this didn't make any difference -- the file remained at ~30% downloaded. I found the .tmp file under "Android/data/org.codepimps.listenup.free/files/downloaded", I take it that this should replaced eventually?
The file has been in this state since 25th April and other podcasts have downloaded successfully in that time.