Many thanks!
I knew i was somewhere on the right track, but got all in a muddle!
Completed task with the following:
$wp_admin_bar->add_menu( array(
'id' => 'support-request',
'parent' => 'custom-support-menu',
'title' => 'Raise Support Request',
'href' => 'mailto:[email protected]?subject=Client%20Website%20-%20 '. get_bloginfo(name) .' %20-%20Support%20Request',
'meta' => array( 'target'=>'_blank' )
) );
