JN added the code to generate the form, and a page with an invocation for an advanced search function in the Victorian Poetry Network site. I added a few bits of CSS to tweak the appearance:
- In wp-content/plugins/vpn-search/vpn-search.css I created four selectors "fieldset", "fieldset div.text", "fieldset label" and "fieldset input[type='submit']"); the last two are the two that really matter.
- In wp-content/plugins/vpn-search/form_advanced.php I added a fieldset around the submit button just for visual consistency

I then added a crude link to the advanced search page (advanced search) in the form.php file which generates the simple search form. I'm not super familiar with Jamie's code and more significantly with the implications of working in the WordPress context, so I'm looking into how to write a more elegant link (e.g. one that preserves the state of the fields in the advanced search form) and whether that's done manually or through the CMS.