I had thought of that one, but was a bit nervous about trying it.
What I've just done...
edit /var/lib/dpkg/info/bastille.prerm so that it always exits 'true'.
This means dpkp -r bastille thinks it has worked.
Unfortunately, it still won't install the newer version, despite doing
a purge first, with the same error as before. I'm a bit more reluctant
to fake bits of that because you risk ending up with networking
disabled.
Ian