Hi Les

I am pretty sure you can just add a filter clause in the same way as the complex table field:

$manager = new FileDataObjectManager(
         $this, // Controller
         'FileResources', // Source name
         'FileResource', // Source class
         'Attachment', // File name on DataObject ( Resource::$has_one = array('Attachment' => 'File') )
         array(
            'DisplayTitle' => 'DisplayTitle'
         ), // Headings
         'getCMSFields_forPopup', // Detail fields (function name or FieldSet object)
         "ServicePageID = $this->ID" //Filter clause ******HERE****** make sure to add the coma above too
         // Sort clause
         // Join clause
      );

Ahahaha!! A cupt of tea and fits into place...

It turns out that I'd declared a has_one relationship in the FileResource class, but had named it Page, not ServicesPage - a simple change in the FileResource class to:

and a quick rebuild of the DB and all is working.

Now, my next question is - do I need to create a Resource class for each of the page types that I want to display this control on, or is there an easy way for me to set the filter on the main page ID? Can I do it through the SiteTree table at all?

Thanks for the nudge Aram, that works perfectly.

1) This is actually in production right now. I've had a number of requests for it. Check out the svn later today (it's Friday morning here). The implementation is $manager->allowUploadFolderSelection();

2) File size and type are stored automatically in the File table. Use $Size and $Type (I believe). In the example code for "Resource" that would look like this:

$Attachment.Size
$Attachment.Type

(might be FileType, or something like that. I forget the exact name of the property)