marksjo on "[Plugin: WordPress SEO by Yoast] %%sitename%% not showing up in category or post titles..."

OK I've managed to fix it. I added the following code to my header.php
<title><?php wp_title(); ?><?php bloginfo('name'); ?></title>
That fixed my pages but doubled up my sitename on the home page. I then went into SEO Titles and Metas and on the Home page tab I set the Title template to read %%sitedesc%% only and this seemed to fix it.