how to group custom post type posts by custom taxonomy terms

I would really appreciate if you could help me 🙂 I’m very stuck and don’t know how to proceed.

I have a custom post type called event and 2 custom taxonomies registered for it:

1. event_type with tag-like functionality (ex. of event type: yoga, voice work)
2. event_location with category-like functionality (ex of event location: uk->brighton, london; europe->paris).

There are pages on the website like Yoga -> Upcoming events; Voice work -> Upcoming workshops. Depending on which page we are on I’d like to display appropriate events. For example, if we’re on page Yoga -> Upcoming events I’d like to display all event custom posts with event_type being yoga and then group the results by event_location taxonomy terms. For example, list all yoga events for UK, Brighton then UK, London and then Europe, Paris and so on.

What I currently do in a template is the following:

1. I get the slug of the current page and its ancestors.
2. I get slugs of all terms in the event_type taxonomy, that have some events associated with them.
3. I determine which event types to display, by intersecting previously gathered values.
4. Then I construct a WP_Query to get event posts with determined event_type taxonomy terms.

This seems to work. However, results came back unordered and I would like them to be ordered by event_location taxonomy terms. For example:

• UK

  • Brighton
    • Event 1
    • Event 2
  • London
    • Event 3

• Europe

  • Paris
    • Event 4

I would also like to display only non-expired event posts and order them by event_date. The event_date value is stored as meta value along with the rest of event post details under a single meta_key.

Here is my code so far:

    //pull in the appropriate events depending on the page type: yoga/voice work
    /* get the ancestors and current page slugs */
    // collect ancestor pages
    $relations = get_post_ancestors($post->ID);
    // add current post to pages
    array_push($relations, $post->ID);
    // get pages slugs
    $relations_slugs = array();
    foreach($relations as $page_ID){
        $page = get_page($page_ID);
        array_push($relations_slugs, $page->post_name);
    }

    /* get the term slugs (non-empty) for event_type taxonomy */
    //get the event_type taxonomy values
    $event_types = get_terms( 'event_type', 'hide_empty=true' );
    $event_types_slugs = array();
    foreach($event_types as $event_type){
        array_push($event_types_slugs, $event_type->slug);
    }

    /* find what event_type to display on the current page */
    $page_event_types = array_intersect($relations_slugs, $event_types_slugs);
    $page_event_types_string = implode(",",$page_event_types);

    /* find the events of the event_type to display on the current page */
    $args = array(
        'post_type' => 'event',
        'tax_query' => array(
            array(
                'taxonomy' => 'event_type',
                'field' => 'slug',
                'terms' => $page_event_types_string
            )
        )
    );
    $temp = $wp_query; //assign orginal query to temp variable for later use   
    $wp_query = null;
    $wp_query = new WP_Query($args);

    /* run the loop to output the event's details */
    get_template_part( 'loop', 'event-details' );

I’m not great at constructing SQL statements. I would really appreciate if you could help me.
Thank you very much!!!

EDIT

I have significantly simplified the functionality (as I got quite confused and lost in the original one). Please see my answer.

Thanks to @Bainternet for taking the time and trying to help me out!