Can't login to phpmyadmin since freepbx install script - open_basedir problems

A few days ago, I followed this excellent, clear guide to installing freePBX (http://wiki.freepbx.org/display/HTGS/Installing+FreePBX+12+on+Ubuntu+Server+14.10#InstallingFreePBX12onUbuntuServer14.10-UpdateYourSystem). It may be coincidence, but since then, I’ve not been able to login to my phpmyadmin which has been installed and working fine for months, installed via this repo:

deb http://ppa.launchpad.net/tuxpoldo/phpmyadmin/ubuntu utopic main

no in-page errors but the logs showed:

PHP message: phpmyadmin: Failed to load /etc/phpmyadmin/config-db.php Check group www-data has read access and open_basedir restrictions"
PHP message: phpmyadmin: Failed to load /var/lib/phpmyadmin/config.inc.php Check group www-data has read access and open_basedir restrictions"

So, I checked:

ll /etc/phpmyadmin

drwxrwxr-x   3 www-data www-data  4096 Nov 16 20:11 ./
drwxr-xr-x 132 root     root     12288 Nov 17 15:33 ../
-rw-r-----   1 www-data www-data   549 Nov 16 20:11 config-db.php

and

ll /var/lib/phpmyadmin

drwxr-xr-x  4 www-data www-data 4096 Oct  8 15:51 ./
drwxr-xr-x 62 root     root     4096 Nov 12 13:10 ../
-rw-r-----  1 www-data www-data 4478 Nov 16 19:48 config.inc.php

I followed this SO answer http://stackoverflow.com/a/24453013/401713 and changed the user and group permissions to match the example (user:root, group:www-data) and changed the directory permissions to match.

I double, triple checked that no open-basedir restrictions are in effect, and I checked phpinfo()
I tried changing the permissions to be that of the fpm worker pool.
I rebooted.
I did an sudo apt-get install --reinstall phpmyadmin.

Everything else, all other sites etc, are running fine. Before I lose any more hair than I have done in the last 5 hours, I’d really appreciate some ideas. As I said, it may be totally unrelated to the freepbx install, which, incidentally, I can’t use anyway as I need to rely heavily on controlplayback and freepbx is missing that so out it goes for now. Looks like a nice script, but it’s no good for my rather niche needs at the moment. Thanks!