Thanks for ypour reply.
This is what I have done since.
NoIP forwards the domain mydomain.servehttp.com to my dynamic ip.
I have set up in 123Reg to forward my domain name mydomain.co.uk to mydomain.servehttp.com that all works fine.
I have now setup ISPConfig with the site mydomian.co.uk, but now when I type in www.mydomain.co.uk
I get the sharedip page. Is there a way around this?