Add terms to taxonomy

Hi,

I am writing a plugin using OOP.

I have a class (activated from the main plugin file by require_once) to create a custom post type and a hierarchal taxonomy and to populate the taxonomy with parent and children terms. The code below works as in the parents (carmakes) are added but when i try to add the children, only the 1st is added. On the taxonomy screen there are 4 pages now visible but they are blank. The database has the children added with the correct parent id……Anyone able to shed some light on this?

class car_post_type {
	var $dname= 'carmarket';
	var $makes= null;
	var $taxonomy = 'carmake';

	public function __construct () {

	$car= new base_posttype ('carmarket', array(
	'has_archive' => TRUE,
			'menu_position' => 11,
			'rewrite' => array(
				'slug' => $dname,
				'with_front' => FALSE,
			),
			'supports' => array( 'title', 'editor', 'thumbnail', 'comments', 'custom-fields', 'revisions' ),
			'menu_icon' => AD_URL . '/resources/img/caricon.png',
));

	$car->add_taxonomy( 'location');

	$car->add_taxonomy ($this->taxonomy, array(
	'hierarchical' => true
	));

	$car->add_meta_box( 'Car_Info' , array(
		'price' => 'text',
		'engine_size' => 'text',
		'fuel_type' => 'text',
		'body_type' => 'text',
		)
	);

	$this->makes = $this->assign_models();

	add_action('init' , array( &$this ,'save_makes' ) );
	add_action('init', array ( &$this, 'save_models'), 100 );

	} // end construct

	public function assign_models() {

		$makes= array (
		'Abarth'=> array('500'),
		'Aixam' => array('Mega City'),
		'Alfa Romeo' => array('146','147','156','159','166','Brera' ,'Giulietta' ,'GT' ,'GTV' ,'Mito','Spider'),
		'Aston Martin' => array ('DB7','DB9','V8','V8'),
		'Audi' => array('80','A1','A2','A3','A4','A5','A6','A7','A8','Allroad','Cabriolet','Q3','Q5','Q7','R8','RS4','RS5','S2','S3','S4','S5','S6','S8','TT'),
		'Austin' => array('Healey','Mini'),
		'BMW' => array('1 Series','2 Series','3 Series','4 Series','5 Series','6 Series','7 Series','i3','i8','X1','X3','X5','X6','Z4')

		);

		apply_filters('carmakes', $makes);

		return $makes;

	}

	public function save_makes () {

		foreach ($this->makes as $make => $models) {
			$term='';
			$terma='';
			$termb='';
			$term= term_exists( $make , 'carmake' );
			if ($term == 0) {
			echo $make;
			echo $advert->post_type_name;
			$y=wp_insert_term ($make, 'carmake' , array('parent' => 0) );
			var_dump($y);
			} 

		}
	}

	public function save_models() {

		foreach ($this->makes as $make => $models) {

			foreach ($models as $model) {

				$term= get_term_by ( 'name', $make , 'carmake' );
				$termexists = get_term_by ('name' , $model, 'carmake' );

				if ( $termexists ) {
					$termexists = $termexists->term_id;
				} else {
					$termexists = null;
				}

				if( ! $termexists ) {
					wp_insert_term ($model , 'carmake', array('parent'=>$term->term_id) );
				}
			}

		}

	}

}
$advert= new car_post_type;