Custom Taxonomy Dropdown in Post edit screen

<?php
/**
 * @package WordPress
 * @subpackage DyneDrewett
 */

/** Remove the 'Sectors' meta box from the edit post screen for the service post type */
add_action('admin_head', 'remove_sectors_taxonomy_box');
function remove_sectors_taxonomy_box(){

    remove_meta_box('tagsdiv-sector', POST_TYPE_SERVICE, 'side');

}

/** Add a custom matabox for placing a service in a sector, and save the options when the user presses 'Publish'/'Update' */
if(current_user_can('manage_categories')) :

    /** Add the sectors dropdown */
    add_action('admin_menu', 'add_sectors_dropdown');

    /** Save the sectors taxonomy data */
    add_action('save_post', 'save_sectors_data');

endif;

/**
 * Create the custom 'Sector' meta box
 */
function add_sectors_dropdown(){

    add_meta_box('sectors-dropdown', __('Sector'), 'do_sectors_dropdown', POST_TYPE_SERVICE, 'side', 'core');

}

/**
 * Populate the custom 'Sector' meta box
 */
function do_sectors_dropdown(){

    global $post;

    /** Create a security nonce for this dorpdown */
    echo '<input type="hidden" name="taxonomy_noncename" id="taxonomy_noncename" value="'.wp_create_nonce('taxonomy_sector').'" />';

    /** Get all sector taxonomy terms */
    $sectors = get_terms(TAXONOMY_SECTOR, 'hide_empty=0');

    /** Get all of this object's terms that are in the 'sector' taxonomy */
    $selected_sectors = wp_get_object_terms($post->ID, TAXONOMY_SECTOR);

    $dropdown = "\n\n".'<select name="sector" id="sector">'."\n";
    $dropdown.= "\t".'<option id="sector-none" value="no-sector">Select a Sector</option>'."\n";
    foreach($sectors as $sector) :
        $selected = (!is_wp_error($selected_sectors) && !empty($selected_sectors) && !strcmp($sector->slug, $selected_sectors[0]->slug)) ? ' selected="true"' : false;
        $dropdown.= "\t".'<option id="sector-'.$sector->term_id.'" value="'.$sector->slug.'"'.$selected.'>'.$sector->name .'</option>'."\n";
    endforeach;
    $dropdown.= '<select name="sector" id="sector">'."\n\n";

    echo $dropdown;

}

/**
 * Save the term that the user selects from the custom 'Sector' meta box
 *
 * @param required integer $post_id The id of the post being edited
 * @return false|string $sector The sector that the user selected
 */
function save_sectors_data($post_id) {

    /** Check the security nonce to ensure we have the proper authorisation  */
    if(!wp_verify_nonce($_POST['taxonomy_noncename'], 'taxonomy_sector')) :
        return false;
    endif;

    /** Ensure that the user has the correct permissions */
    if(!current_user_can('edit_post', $post_id)) :
        return false;
    endif;

    /** Check if this is an auto save routine. If it is our form has not been submitted, so we dont want to do anything */
    if(defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) :
        return false;
    endif;

    /** Now save the data against the correct taxonomy */
    $post = get_post($post_id);
    if($post->post_type === POST_TYPE_SERVICE) :
        $sector = $_POST[TAXONOMY_SECTOR];
        wp_set_object_terms($post_id, $sector, TAXONOMY_SECTOR);
    endif;

    return $sector;

}
?>