Convert from HeadSpace2 to Yoast SEO quick.

szbl-seo-converter.php

<?php
/*
  Adds Yoast SEO post meta for quick conversion for title/meta description
  from HeadSpace2.
*/

add_action( 'init', 'szbl_convert' );

function szbl_convert()
{
	if ( $_GET['seo-conversion'] == 1 )
	{
		echo '<div style="font:16px Helvetica,Arials,Sans-serif;">';

		$posts = new WP_Query(array( 'post_type' => array( 'post', 'page' ), 'posts_per_page' => 999 ) );
		while ( $posts->have_posts() )
		{
			$posts->the_post();

			$title = get_post_meta( get_the_ID(), '_headspace_page_title', true );
			$description = get_post_meta( get_the_ID(), '_headspace_description', true );

			update_post_meta( get_the_ID(), '_yoast_wpseo_title', $title );
			update_post_meta( get_the_ID(), '_yoast_wpseo_metadesc', $description );

			echo '<h1>' . get_the_title() . '</h1>';
			echo '<h3>' . $title . '</h3>';
			echo '<p><em>' . $description . '</em></p>';
			echo '<hr>';
		}

		echo '</div>';
		die;
	}
}