Many thanks to you both. I prefer the all-Debian package solution simply because anything I do at a command prompt is performed as a recipe in total ignorance of its meaning. I am unfamiliar with kpackage, so that seems like a good first step.
OG.
Update: Well kpackage didn't work for me on this. I didn't understand what to do in the 'Settings', amongst other things.
I tried apt-get install mozilla-thunderbird. It stalled on 'getting headers', then suggested doing an apt-get update. This stuck on 'getting headers' at 28%. Not having much joy this morning! More suggestions?