PHP/MYSQL code to display custom posts with certain characteristics

I am rebuilding a Wordpress based website but I am struggling to get a section of it working correctly.

The "members" are a custom post type in Wordpress with a number of different characteristics set up within each post type (eg region, type).

At the moment the member directory is simply an alphabetical list of all members (ie all custom posts of the type "member"). I want to be able to display a list of a selection of custom posts of the type "member" that have a certain characteristic eg all members in Southern England.

The current code for pulling the members is: <ul>
<?php $loop = new WP_Query( array( 'post_type' => 'member', 'posts_per_page' => 500, 'orderby' => 'title', 'order' => 'ASC' ) ); ?>

<?php while ( $loop->have_posts() ) : $loop->the_post(); ?>
<li>

Please could you quote me for giving me two replacement for the above code that will pull all members that have

1) one specific characteristic - eg are in Southern England
2) two specific characteristics - eg are in Southern England and are a Distributor-Manufacturer

I have all the templates working fine, but it's just the replacement code for the above code to go onto the template that I need please.

Ideally you'd be able to complete this job within the next 48 hours please. I can provide more info on the system names etc within the custom post types. The post types were set up with the "Easy Post Type" wordpress plugin.

thanks
sw