I'm about 1/3 of the way there...
The templates for RC are not what I was expecting but I'll crack on again tomorrow. Also I suspect that we'll have to add the HTML headers to the email. Not <HTML>
etc but $headers = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";