Entity form in ctools modal popup, whilst passing in values from current node
If anyone's interested in the answer, I just appended ?nid=5 to the end of the link url. Then I could just hook_form_alter to get the nid:

if($form['#id'] == 'whatever-entityform-edit-form'){

        $nid = $_GET['nid'];
        $node = node_load($nid);

        $form['field_whatever'][LANGUAGE_NONE][0]['target_id']['#default_value'] = "$node-&gt;title ($node-&gt;nid)";

    }


Might not be the best way, but it works.