I've actually found several tmp directories (writable by everyone): /home/virtual/site22/fst/tmp /home/virtual/site22/fst/var/tmp

I'm not permissioned to write to /var/www/

I wonder if there is somewhere I can tell the mediawiki installer to use on of those tmp directories.

If I'm not mistaken you need the tmp-directory in your virtual host setting to be writeable by your apache user. Maybe you got a tmp directory like so /home/virtual/site22/fst/var/www/tmp in the virtual_host config of your account (So it's outside docroot). That virtual host directory may have permissions like drwxr_xr_x or just drwx______ with you as owner and ftpuser as group. That's something the apache user won't have any write permissions to. If so, you can give that tmp directory write permissions like 777 or ask your provider to do a chown apache-user.apache-user (www-data in my case) to that tmp directory and it should work.

But that would mean your VirtualHost setup is being a poor, sad story. I.e. not real useful.

--tictric