Hay men, i've got a general navigation which appears like this:

PAGE 1
    PAGE 1.1
        PAGE 1.1.1
        PAGE 1.1.2
    PAGE 1.2
        PAGE 1.2.1

I wish to display a hyperlink on pages 1.1.1, 1.1.2 and 1.2.1. As you can tell they are childrens' kids of the primary navigation.

Wouldso would i actually do this in WordPress?

Use following code snippet inside the loop to do this objective:

<?php
if ($post->post_parent) {
   $parent = get_page($post->post_parent);
   $parentLink = get_permalink($parent->ID);

   if ($parent->post_parent) {
      $grandParent = get_page($parent->post_parent);
      $grandParentLink = get_permalink($grandParent->ID);
   }
}

// display the links to parent and grand parent pages now
echo $parentLink . ' | ' . $grandParentLink;
?>

what about simply using:

<?php if( is_page('PAGENAME') ) { ?>
   <a href="#">Your Link</a>
<?php } ?>

then your link are only proven on that page...if you would like it on the couple of different pages then:

<?php if( is_page('PAGENAME') || 
          is_page('OTHERPAGE') || 
          is_page('ANOTHERPAGE') 
        ) { ?>
   <a href="#">Your Link</a>
<?php } ?>

this normaly works suitable for me for which i want it to complete..