Telling cakePHP to render as XML / use xml/blah.ctp instead of blah.ctp

I have been successfully using XML view files in CakePHP (request the XML output type in headers so CakePHP will use e.g. Orders/xml/create.ctp instead of Order/create.ctp).

However, now i need to add some functionality that requires me to the reformat the XML at the end of most business logic in the controller.

So i tried this in the controller action:

public function createorder() {
    $this->autoRender = false; // disable automatic content output
    $view = new View($this, false); // setup a new view

    { ... all kinds of controller logic ...}

    { ... usually i would be done here and the XML would be outputted, but the autorender will stop that from happening ... }

    { ... now i want the XML in a string so i can manipulate the xml ... }
   $view_output = $view->render('createorder'); // something like this

}

But what this gives me is:

<?xml version="1.0" encoding="UTF-8"?>
 <response>
  <error>View file &amp;quot;/Users/test/Documents/hosts/mycakeapp/app/View/Orders/createorder.ctp&amp;quot; is missing.</error>
  <name>MissingViewException</name>
  <code>500</code>
  <url>/orders/createorder/</url>
 </response>

So i need to tell CakePHP to pickup the xml/createorder.ctp instead of createorder.ctp. How do i do this?

Cheers!