OK, think I’ve sorted it, but perhaps not the correct way(?)
My header.php <head> is the following:
<head>
<title><?php bloginfo('title'); ?></title>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="<?php bloginfo('template_url'); ?>/js/jquery-1.8.3.min.js"></script>
<script type="text/javascript" src="<?php bloginfo('template_url'); ?>/css/5grid/init.js?use=mobile,desktop,1000px"></script>
<script type="text/javascript" src="<?php bloginfo('template_url'); ?>/js/init.js"></script>
<link rel="stylesheet" href="<?php bloginfo( 'template_url' ); ?>/css/spreadsheet.css" type="text/css" />
<link rel="stylesheet" href="<?php bloginfo( 'template_url' ); ?>/style.css" type="text/css" />
<?php wp_head(); ?>
</head>
