gistfile1.php

<?php
$term = get_term_by( 'slug', get_query_var( 'pro' ), "post_tag" );
$tagslug = $term->slug;
$ukposts = get_posts( array(
	'posts_per_page' => -1,
	'post_type' => 'uk', 
	'post_status' => 'publish'
) );
$proposts = get_posts( array(
	'posts_per_page' => -1,
	'post_type' => 'post', 
	'tag' => $tagslug, 
	'post_status' => 'publish'
) );
$merged_IDs = array_merge( 
	wp_list_pluck( $proposts, 'ID' ),
	wp_list_pluck( $ukposts, 'ID' ) 
);

$merged_IDs = array_unique($merged_IDs);
$posts = get_posts( array( 
	'post_type' => array( 'uk', 'post' ),
	'post__in' => $merged_IDs, 
	'post_status' => 'publish'
) );
foreach($posts as $post) :
setup_postdata($post);
var_dump($post); 
endforeach; ?>