I have now worked out where my front page comes from, it's generated by the Views module, I couldn't find it originally because Home » Dashboard » Site building » Views was disabled.
So the page is basically created by a Filters entry in the View with various Taxonomy entries to enable users to select what they want and a Node to generate the data.
The problem I'm seeing is that the Taxonomy filter entry on screen isn't 'folding away' as it should. This has happened since updating Drupal core from 6.16 to 6.22 and updating all the modules to get rid of many security warnings.
To see what I mean the old/correct front page is:-
http://globaloptimists.isbd.net/
While the new/wrong front page is:-
http://www.globaloptimists.org/
Is this a bug, a misconfiguration, or what?