Thank you for your post.
When you turn on Instant Web Publishing, FileMaker displays the IP address of that machine. If you then launch a browser and enter:
You will see the Instant Web Publishing screen with your database listed (provided you set it to All users access).
If you want to share this for others outside the network, you will have to contact your service provider and acquire a static IP Address. Or, there are several services that host FileMaker solutions for the web. Use your favorite web search engine and search for "FileMaker Hosting". This will give you a good starting point. Also, I believe there are some forum members here who also provide FileMaker hosting.
I finally did the obvious - asked the guy I pay for tech support and he pointed out that I needed to configure my router/adsl access to make the IP address available over the internet - all is now working fine!
However, I appreciate the answer and the assistance it offered, great forum!