Stop certain posts from appearing on home page ?

I am trying to stop certain posts from appearing on the front page of www.mummybird.com

I have created a page for reviews as I don't want the reviews clogging up the home page.

I've added this to the index.php
<?php if (is_front_page() && !is_paged() )
$posts = query_posts($query_string . '&cat=-108'); ?>

It works on the first home page but the review posts then start appearing on the second page. It's also started doubling posts that appear on the first page and putting then on the second page again.

Anybody got any suggestions how I can make this happen ?

thanks Jon