Ooh, interesting one... you can 100% rule out a cache problem - I can see where the map is supposed to be on the page, but you're right - it's not there.. However, the file has been published to the server... this is its location:
http://www.skipworths.talktalk.net/arthogsteam/How_to_find_us_files/widget0_mark up.html
Widget Mark Up HTML pages are published by iWeb to display the widget contents, and the widget simply pulls through the contents onto the main page.
The problem seems to be that the widget on your Contact Us page isn't pulling the map through from the widget markup page...
I've checked View Source on both pages and from what little I know of html, I can't see anything wrong there either. (any hardcore HTMLer's out there - please double check !)
When you published the site, did you "Publish Site Changes" or "Publish Entire Site"?
If you didn't Publish the Entire site - have a go at that first and let me know what happens.
R
P.S. I'm from Swansea originally 8-)