Finally solved it! I needed to add this at the end of each loop 🙂
<?php $my_query = new WP_Query(array( 'category_name' => get_post_meta($post->ID, 'featured', true), 'posts_per_page' => 5, )); if ($my_query->have_posts()): ?>
<?php while ($my_query->have_posts()) : $my_query->the_post(); ?> content etc goes here
<?php endwhile; ?> <?php endif; ?><?php wp_reset_query(); ?>
many thanks
James