You did it wrong way. You should have an option to manage nameservers / DNS for your domain name through which you need to change nameservers of your domain. Forwarding option will redirect your domain name to the default apache page of server and that wont work.
If you find it difficult to change the nameservers then open a ticket for me in sales department and let me know the login details of your 123-reg account. I will do the needful for you. You can open ticket from
http://support.eukhost.com
You may feel somewhat uncomfortable right now but we are here to set you up for smooth hosting experience.