KCFinder Integration

I'm trying to integrate KCFinder with CKEditor under Zen 1.5.1. Whatever I do I keep getting the error  "You don't have permission to access /editors/ckeditor/kcfinder/upload.php on this server". I'm using Session Configuration and have set the local values using core/autoload.php. I've set file permissions to 777 so that shouldn't be an issue.

Config.php is as follows

<?php

/** This file is part of KCFinder project
  *
  *      @desc Base configuration file
  *   @package KCFinder
  *   @version 2.51
  *    @author Pavel Tzonkov <pavelc@users.sourceforge.net>
  * @copyright 2010, 2011 KCFinder Project
  *   @license http://www.opensource.org/licenses/gpl-2.0.php GPLv2
  *   @license http://www.opensource.org/licenses/lgpl-2.1.php LGPLv2
  *      @link http://kcfinder.sunhater.com
  */

// IMPORTANT!!! Do not remove uncommented settings in this file even if
// you are using session configuration.
// See http://kcfinder.sunhater.com/install for setting descriptions

$_CONFIG = array(

    'disabled' => true,
    'denyZipDownload' => false,
    'denyUpdateCheck' => false,
    'denyExtensionRename' => false,

    'theme' => "oxygen",

    'uploadURL' => "http://www.shortgrass.co.uk/editors/ckeditor/kcfinder/upload",
    'uploadDir' => "",

    'dirPerms' => 0755,
    'filePerms' => 0644,

    'access' => array(

        'files' => array(
            'upload' => true,
            'delete' => true,
            'copy' => true,
            'move' => true,
            'rename' => true
        ),

        'dirs' => array(
            'create' => true,
            'delete' => true,
            'rename' => true
        )
    ),

    'deniedExts' => "exe com msi bat php phps phtml php3 php4 cgi pl",

    'types' => array(

        // CKEditor & FCKEditor types
        'files'   =>  "",
        'flash'   =>  "swf",
        'images'  =>  "*img jpg gif png",

        // TinyMCE types
        'file'    =>  "",
        'media'   =>  "swf flv avi mpg mpeg qt mov wmv asf rm",
        'image'   =>  "*img",
    ),

    'filenameChangeChars' => array(/*
        ' ' => "_",
        ':' => "."
    */),

    'dirnameChangeChars' => array(/*
        ' ' => "_",
        ':' => "."
    */),

    'mime_magic' => "",

    'maxImageWidth' => 0,
    'maxImageHeight' => 0,

    'thumbWidth' => 100,
    'thumbHeight' => 100,

    'thumbsDir' => ".thumbs",

    'jpegQuality' => 90,

    'cookieDomain' => "",
    'cookiePath' => "",
    'cookiePrefix' => 'KCFINDER_',

    // THE FOLLOWING SETTINGS CANNOT BE OVERRIDED WITH SESSION CONFIGURATION
    '_check4htaccess' => true,
    //'_tinyMCEPath' => "/tiny_mce",

    //'_sessionVar' => &$_SESSION['KCFINDER'],
    //'_sessionLifetime' => 900,
    //'_sessionDir' => "/var/www/vhosts/webmaven.co.uk/zen/cache",

    //'_sessionDomain' => ".www.shortgrass.co.uk",
    //'_sessionPath' => "/zen_admin",
);

?>

core/autoload.php is set as follows:-

<?php

/** This file is part of KCFinder project
  *
  *      @desc This file is included first, before each other
  *   @package KCFinder
  *   @version 2.51
  *    @author Pavel Tzonkov <pavelc@users.sourceforge.net>
  * @copyright 2010, 2011 KCFinder Project
  *   @license http://www.opensource.org/licenses/gpl-2.0.php GPLv2
  *   @license http://www.opensource.org/licenses/lgpl-2.1.php LGPLv2
  *      @link http://kcfinder.sunhater.com
  *
  * This file is the place you can put any code (at the end of the file),
  * which will be executed before any other. Suitable for:
  *     1. Set PHP ini settings using ini_set()
  *     2. Custom session save handler with session_set_save_handler()
  *     3. Any custom integration code. If you use any global variables
  *        here, they can be accessed in config.php via $GLOBALS array.
  *        It's recommended to use constants instead.
  */

// PHP VERSION CHECK
if (substr(PHP_VERSION, 0, strpos(PHP_VERSION, '.')) < 5)
    die("You are using PHP " . PHP_VERSION . " when KCFinder require at least version 5! Some systems has an option to change the active PHP version. Please refer to your hosting provider or upgrade your PHP distribution.");

// GD EXTENSION CHECK
if (!function_exists("imagecopyresampled"))
    die("The GD PHP extension is not available! It's required to run KCFinder.");

// SAFE MODE CHECK
if (ini_get("safe_mode"))
    die("The \"safe_mode\" PHP ini setting is turned on! You cannot run KCFinder in safe mode.");

// CMS INTEGRATION
if (isset($_GET['cms'])) {
    switch ($_GET['cms']) {
        case "drupal": require "integration/drupal.php";
    }
}

// MAGIC AUTOLOAD CLASSES FUNCTION
function __autoload($class) {
    if ($class == "uploader")
        require "core/uploader.php";
    elseif ($class == "browser")
        require "core/browser.php";
    elseif (file_exists("core/types/$class.php"))
        require "core/types/$class.php";
    elseif (file_exists("lib/class_$class.php"))
        require "lib/class_$class.php";
    elseif (file_exists("lib/helper_$class.php"))
        require "lib/helper_$class.php";
}

// json_encode() IMPLEMENTATION IF JSON EXTENSION IS MISSING
if (!function_exists("json_encode")) {

    function kcfinder_json_string_encode($string) {
        return '"' .
            str_replace('/', "\\/",
            str_replace("\t", "\\t",
            str_replace("\r", "\\r",
            str_replace("\n", "\\n",
            str_replace('"', "\\\"",
            str_replace("\\", "\\\\",
        $string)))))) . '"';
    }

    function json_encode($data) {

        if (is_array($data)) {
            $ret = array();

            // OBJECT
            if (array_keys($data) !== range(0, count($data) - 1)) {
                foreach ($data as $key => $val)
                    $ret[] = kcfinder_json_string_encode($key) . ':' . json_encode($val);
                return "{" . implode(",", $ret) . "}";

            // ARRAY
            } else {
                foreach ($data as $val)
                    $ret[] = json_encode($val);
                return "[" . implode(",", $ret) . "]";
            }

        // BOOLEAN OR NULL
        } elseif (is_bool($data) || ($data === null))
            return ($data === null)
                ? "null"
                : ($data ? "true" : "false");

        // FLOAT
        elseif (is_float($data))
            return rtrim(rtrim(number_format($data, 14, ".", ""), "0"), ".");

        // INTEGER
        elseif (is_int($data))
            return $data;

        // STRING
        return kcfinder_json_string_encode($data);
    }
}

// CUSTOM SESSION SAVE HANDLER CLASS EXAMPLE
//
// Uncomment & edit it if the application you want to integrate with, have
// its own session save handler. It's not even needed to save instances of
// this class in variables. Just add a row:
// new SessionSaveHandler();
// and your handler will rule the sessions ;-)

class SessionSaveHandler {
    protected $savePath;
    protected $sessionName;

    public function __construct() {
        session_set_save_handler(
            array($this, "open"),
            array($this, "close"),
            array($this, "read"),
            array($this, "write"),
            array($this, "destroy"),
            array($this, "gc")
        );
    }

    // Open function, this works like a constructor in classes and is
    // executed when the session is being opened. The open function expects
    // two parameters, where the first is the save path and the second is the
    // session name.
    public function open($savePath, $sessionName) {
        $this->savePath = $savePath;
        $this->sessionName = $sessionName;
        return true;
    }

    // Close function, this works like a destructor in classes and is
    // executed when the session operation is done.
    public function close() {
        return true;
    }

    // Read function must return string value always to make save handler
    // work as expected. Return empty string if there is no data to read.
    // Return values from other handlers are converted to boolean expression.
    // TRUE for success, FALSE for failure.
    public function read($id) {
        $file = $this->savePath . "/sess_$id";
        return (string) @file_get_contents($file);
    }

    // Write function that is called when session data is to be saved. This
    // function expects two parameters: an identifier and the data associated
    // with it.
    public function write($id, $data) {
        $file = $this->savePath . "/sess_$id";
        if (false !== ($fp = @fopen($file, "w"))) {
            $return = fwrite($fp, $data);
            fclose($fp);
            return $return;
        } else
            return false;
    }

    // The destroy handler, this is executed when a session is destroyed with
    // session_destroy() and takes the session id as its only parameter.
    public function destroy($id) {
        $file = $this->savePath . "/sess_$id";
        return @unlink($file);
    }

    // The garbage collector, this is executed when the session garbage
    // collector is executed and takes the max session lifetime as its only
    // parameter.
    public function gc($maxlifetime) {
        foreach (glob($this->savePath . "/sess_*") as $file)
            if (filemtime($file) + $maxlifetime < time())
                @unlink($file);
        return true;
    }
}

new SessionSaveHandler(user);

// PUT YOUR ADDITIONAL CODE HERE
ini_set('session.gc_maxlifetime', '900');
ini_set('session.save_path', '/var/www/vhosts/webmaven.co.uk/zen/cache');
ini_set('session.cookie_domain', '.www.shortgrass.co.uk
ini_set('session.cookie_path', '/zen_admin');
ini_set('session_cookie_httponly', 'On');
ini_set('session.gc.divisor', '2');
ini_set('session.name', 'zenAdminID');
ini_set('session.save.handler', 'user');
?>

Any suggestions or ideas?