Web publishing with MS Proxy2

I have MS Proxy 2, IIS4 and Exchange 5.5 all on a NT4 PDC. We use a Cisco 2500 router and intend to host or own site. Proxy has already been succesfully setup to allow E-mail and intranet browser access to the internet is fine. All local clients cansee default intranet site by typing in the www.XXXX.co.uk but Internet clients attempting to access the same get “unknown host” error message. Ports 80 and 443 for HTTP and HTTPS are allowed as is “Enable Web Publishing”. Our Domain name is registerd. I’ve been thru the usual points outlined in other Q&A on simmilar subjects but still cant get it to work.
Any ideas??