First, login to your billing account in the Client Area from the below links.
North Hosts: https://nh.ukhost4u.com/clientarea/clientarea.php
Go to “Domains > My Domains”, and click the ACTIVE button beside the domain name.
Then select “Nameservers” on the left hand side underneath Actions:
You’ll then see the current nameservers for your domain name.
To change these, simply enter the new nameservers and click “Change Nameservers”: