Using nodereference field to generate page title with automatic nodetitles module

I've been trying to achieve this for a while now but can't figure out how to do it.
I am building a site that sells football tickets.
The admin of the site will be able to add clubs, venues and competions using forms built with cck.
The admin will then be able to create a ticket using nodereferences for - home team, away team, venue and competiton. Plus add the date of the event and the cost of a ticket.
I'd like to get automatic nodetitles to use the home team and away team fields to create the page's title.
I haven't been able to manage this yet, only getting as far as getting an output of "Array Vs Array" when I use the following:

<?php
  global $form_values;
  $title = $form_values['field_home_team'] . ' Vs ' .$form_values['field_away_team'];
  return $title;
?>

I know a little PHP, but not enough to figure out what I'm doing wrong here.
Any help is greatly appreciated.