Back in business. There was detritus from previous installs interfering with new installs.
So, the culprit is not uwsgi: unjustly accused. Apologies. File based config is inherently fragile. Uninstalling with apt-get --purge remove uwsgi, etc. was the only way to really start fresh. I think the scripts need to be more robust to deal with upgrade in place scenarios, not just new "from-scratch" installation. --
