Thanks! The application form is actually the newest part of the site (posted last night!). The form itself is just straight HTML (but generated from an XSLT template matching those specific pages on an XML file that maps every page on the site.
The search function (top-left) is courtesy of Atomz, although I hope to create one myself one day - I'm just worried that it might be slow using XSLT.
The site index page is generated from the aforementioned XML file that maps all the pages, for example:
<page id="home" href="index.asp">
<title>Pimlico School - Home Page</title>
<p>Welcome to Pimlico School. Check out our headmaster's <cross ref="about-us-headmasters-welcome">mug shot</cross>.</p>
<page id="about-us" href="about/intro.asp">
... etc ...
That's a simplified version, each <page> actually contains much more detail.
Hope I've managed to explain it clearly enough.