Did I install this correctly? Using 1and1 hosting

Hello,

I recently installed WordPress to my client’s 1and1 hosting account, and the site works fine when browsing to the 1and1 subdomain (e.g. http://s**********.websitehome.co.uk/wordpress), and I can even get to the site fine using the full/proper domain name.

However when clicking on any of the links in the navigation, the URL switches back to the http://s**********.websitehome.co.uk subdomain, when it SHOULD use the proper domain I have.

When I contacted 1and1 they basically said that I had “installed WordPress under the subdomain” – this is what I have done many times with other hosts (Zen, Godaddy etc) but for some reason with 1and1 I’m getting the issue above.

I should also point out that when changing the “Siteurl” and “wordpress url” settings within WordPress, this just causes a “Internal Server error 500” and I have to manually change the domains back to the subdomain within the database.

Hope someone can help?