No worries I found the answer, instead of using get_the_category, I used php functions to split the url up to see the end bit (the slug of the category) and then get the stuff based on that, below is my new code:
<?php
get_header();
get_sidebar();
?>
<div id="content">
<?php
$self = $_SERVER['PHP_SELF'];
$self = basename($self);
$catinfo = get_term_by('slug', $self, 'category');
$catslug = $catinfo->slug;
$catid = $catinfo->term_id;
$catname = $catinfo->name;
?>
<div id="contentheader"><?php echo $catname ?></div><!--END #contentheader-->
<p>
<?php
if($catslug == 'news'){
$myposts = get_posts('numberposts=3&offset=0&'.$catshow);
foreach($myposts as $post): ?>
<li><a href="<?php the_permalink(); ?>"><?php the_title();?></a></li>
<?php endforeach; ?>
<?php }else{
wp_list_categories('title_li=&hide_empty=0&child_of='.$catid);
?>
<?php } ?>
</p>
<?php get_footer(); ?>
