I had the same concern when ordering from Happ. From their website:
A few concerns have come up from our customers about the security of the e-happ system. The reason that the icon for the Secure Lock SSL (Secure Socket Layer) is not showing up is because it is in a frames setup. To verify that checkout that it is running over SSL what can be done is to open the page in a new window.
For Netscape Users: When the checkout page loads up, right click on it and a menu will appear, there will be an option to open it into a new window. Then the new window will have the security icon.
For Internet Explorer Users: When at the cart status page, right click on the checkout button, a menu will appear, there will be an option to 'open link in new window'. The checkout page will load up in the new window, and will have the security icon. Or at the checkout page, simply right click on, a menu will appear, go to properties. There should be a pieces of information: protocol, type, connection. Next to connection it will show that it is running over SSL as well.
But yes Happ are sound, but I have found ordering stuff to the UK costs loads. They add 'duty', carriage and VAT. The final cost is like double what you think it will be...