osCommerce... all you need to do is configure the site
That sounds easy, it infers that all you need to do is click on some options, and voila the site you want is there.
In reality this is not the case. To change the default osCommerce installation into something suitable for a professional UK business there's a lot more that needs to be done, which usually involves getting your hands dirty changing PHP code, CSS code, MySQL, etc.
Even the simplest of visual changes may require editing PHP programming code.
There are contributions that need integrating, for example, autothumbnailing to allow you to have larger product images whilst at the same time having smaller quality fast loading thumbnailing images. Note the use of the word integrating, this is not a simple install program, integrating = following instructions on what pieces of code to change. Other features/contribution, apart from auto-thumbnailing, that usually need adding include SEO, security, PayPal IPN, product option stock control, replacing US speak with UK speak, removing clutter from the interface etc.
To go the DIY osCommerce route you really need to have technical skills like PHP/HTML/CSS/mySQL, or pay someone who does.
If you want to see what osCommerce looks like in its default installation state have a look at:
www.opensourcecms.com
where you can see the default osCommerce installation as a user and as an admin, then try to change how the site looks from the admin screen, you wont get far without delving into code.
Note that the default shop has product images the same size as the thumbnail images so when you click on image to enlarge you get an image exactly the same size, this is to hide the fact that it doesn't have an autothumbnailing feature, the same is true for ZenCart, a derivative of osCommerce, and templatemonster osCommerce templates (which are custom installations of osCommerce with code changes to make the site look different - they are not skins that you easily apply to your existnig osCommerce installation).
To see what we've done with our custom version of osCommerce have a look at:
www.awebapart.com/home/sitebuilder_features
and
www.awebapart.com/home/portfolio_of_client_sites