No, there is no duplicate content, zoflora. As a default, when you go to:
http://www.harlequincakes.co.uk
It will try to display the file index.html or index.htm. This is how the web server hosting software is set up. Other "default" filenames can be commonly used, such as home.html/home.htm or even: default.html or default.htm. If there is no index.html or other default file, then you will get an error message.
When you click on the link on the page, it will direct you to the full URL, or address, the link is set up to direct to, which would be the full address of the page:
www.harlequincakes.co.uk/index.html
If you really wanted to, you could type www.harlequincakes.co.uk/index.html in the address bar of the router, it just isn't necessary.
