Need www on URL to show to use SSL certificate

[MattBUK]

I am in the middle of developing a Zencart site and just purchased a SSL Certificate in the form of www.mysite.co.uk.

However once I have enabled the site to use SSL it is looking for the the certificate in the form of just mysite.co.uk with no www.

I have spoke to the hosting company to try and change this but they said that it is best and most common to use the www.mysite.co.uk format and to go into the settings and specify zencart to use a www. prefix.

I have tried forcing the site to do this using this code in the htdocs

RewriteEngine On
RewriteCond %{HTTP_HOST} ^mysite.co.uk$
RewriteRule ^(.*)$ http://www.mysite.co.uk/$1 [R=301,L]

But the site will not work properly in the checkout it just refreshes the 1st page

Is there a setting in Zencart which can change the entire site to use www or a simple way of doing it that will make the site still work?

I am using 1.3.8 and the basic credit card module

[barco57]

In the includes/configure.php and admin/includes/configure.php make sure the defines for 'HTTP_SERVER' and 'HTTPS_SERVER' have the www. in them