Change Wordpress URL

Hi guys,

i have a wordpress retailer theme site http://csj.uk.com and i also have a second domain csjbespoke.co.uk, and I want the URL in the address bar to show csjbespoke.co.uk and not csj.uk.com.

I have pointed the records to the same address as the current site and in cpanel (version 56.0.28) created an alias and pointed it to the current site.

The site forwards ok but the url changes to csj.uk.com.

When i change the wordpress address url in the general/settings, the admin page then points to csjbespoke.co.uk so thats fine, but when i change the site address url the page is unavailable.

I have checked its not hardcoded in the wp-options or the functions php files.

in the htaccess it shows
RewriteCond %{HTTP_HOST} ^csjbespoke\.co\.uk$ [OR]
RewriteCond %{HTTP_HOST} ^www\.csjbespoke\.co\.uk$
RewriteRule ^/?$ "http\:\/\/csj\.uk\.com\/" [R=301,L]

kind of at a loss as to what to do next, so any help will be great.

regards

phil