You can obviously manually flush the catalog images cache by going to Cache management and clicking on "Flush Catalog Images Cache". My question is can this be set as a scheduled task? If so, what would the code be to create this and what file would it be inserted into?
The below extension looks like it will do what I'm after and a bit more, so will possibly just go with that unless there are any suggestions of a better way to do?
http://www.magentocommerce.com/magento-connect/cron-cache-cleaner-3782.html