Changing Database

I recently installed piwik for my web site and had issues from my host. During this time it appeared I lost my visitor logs however; a dig around my site I noticed that there were multiple databases installed. It appears that during my support issues they had in effect re-installed piwik which created numerous databases.

The bulk of the visitors logs are in the original database but I cannot seem to change the database that the dashboard is linked to (from the dashboard). I have modified the config file and yet it always appears to point to the same database. Anyone got any pointers? how do you find out via the dashboard which database it is actually reporting the data from? Ideally I would like to be able to merge the data in the databases, is there an easy way to do this?