Sort posts in category by custom field

Hi all,

I’d like to be able to allow end users to determine the order in which posts are displayed, particularly when using the category template, by adding a custom field, Order, which has a value of A, B, C etc etc.

The following code works just fine, but would need to be manually altered each time the user wanted a new category:

<?php
$the_query = new WP_query( array ( 'category_name' => 'test', 'orderby' => 'meta_value', 'meta_key' => 'Order', 'order' => 'ASC' )  );
while ($the_query->have_posts()) : $the_query->the_post();
get_template_part( 'content_issue_summary', get_post_format() );
endwhile;
wp_reset_query();
?>

I’ve been trying to alter the category template such that I can create a variable called $cat_name and give it the value of single_cat_title(), then use that to replace ‘test’ – but it’s not working. Any suggestions?