BuddyPress.org

I have the following code creating a custom buddypress menu item no problem.

function mb_bp_profile_menu_posts() {
	global $bp;
	bp_core_new_nav_item(
	array(
	'name' => 'Member Directory',
	'slug' => 'directory', 
        'parent_url' => $bp->loggedin_user->domain . '/' ,
	'position' => 40, 
	'default_subnav_slug' => 'directory', 
	'screen_function' => 'wbc_member_directory'
	)
	);
}
add_action('bp_setup_nav', 'mb_bp_profile_menu_posts', 301 );

/* we're building 2 sub item
 * the first is the one showing by default
 */

function mb_bp_profile_submenu_posts() {
	global $bp;
	if(!is_user_logged_in()) return '';
	bp_core_new_subnav_item( array( 
	'name' => 'WBC Members',
	'slug' => 'directory', 
	'parent_url' => $bp->loggedin_user->domain . $bp->bp_nav['directory']['slug'] . '/' ,
	'parent_slug' => $bp->bp_nav['directory']['slug'],
	'position' => 10,
	'screen_function' => 'wbc_member_directory' //the function is declared below
	) 
	); 

}
add_action('bp_setup_nav', 'mb_bp_profile_submenu_posts', 302 );

/* here we control our 1st sub item
 * first function is the screen_function
 * second function displays the content
*/
function wbc_member_directory(){	
	add_action( 'bp_template_content', 'mb_show_posts' );
	bp_core_load_template( apply_filters( 'bp_core_template_plugin', 'buddypress/members/single/plugins' ) );
}
function mb_show_posts() {
	echo 'TEST';
	// add yout stuff here
}

I can only get it to output text e.g. ‘TEST’ on the page itself. I want to pump in the member directory. Any help please? Pretty sure its a function, action or hook?!