Found this post on the Cocoon gmane list that may be very useful:

With a clear cache action you can clear (most) caches.

In the components:
  <map:actions>
    <map:action name="clear-cache" logger="sitemap.action.clear-cache" src="org.apache.cocoon.acting.ClearCacheAction"/>
  </map:actions>

<!-- ... -->
In the pipelines:
		
  <map:pipeline type="noncaching" internal-only="false">
    <map:match pattern="clearcache.html">
      <map:act type="clear-cache">
        <map:generate src="status" type="status"/>
        <map:serialize type="xml"/>
      </map:act>
    </map:match>
  </map:pipeline>

The value of this may come when we have XUpdate actions which write configuration and preference information to the database; any pipeline which does this could invalidate the cache immediately afterwards, so any changes would take effect.