Hi Mike,
To use SSL on your site you would require a dedicated IP and SSL certificate. The current annual costs for these are £19.95+VAT for the dedicated IP and £34.95+VAT for the SSL certificate. To set up the SSL certificate we will require some additional information which you can find here:
http://www.nethosted.co.uk/blog/interne ... ertificate
These can be added to a plan at any time, so you could set up the site initially without these and add them later, once you add them you'll need to change a setting in Joomla to enable the secure login over https.
One thing to note is that these can only be added to the main domain on a shared hosting account, if multiple sites require SSL certificates you would need to look at a reseller hosting account which allows this.
Regards,
Darryl