The main concept that is preventing your page from working is variable persistence.
when the page loads, you are passing it a querystring variable:
the action of the form does not pass that querystring variable though, so look at it this waY
Page Loads (fld_id=23) shows the correct recordset info.
Submit Form, action is direct_enquiry.php this reloads the page, but the fld_id querystring is not present, so the recordset is empty.
the form has been submitted, so it triggers the email behavior, but the recordset is empty so it's not working.
use the following code for the form action to force it to retain the querystring variable:
action="<?php echo (htmlentities($_SERVER["PHP_SELF"], ENT_QUOTES)); ?><?php echo (isset($_SERVER["QUERY_STRING"]) && $_SERVER["QUERY_STRING"] != ""?"?".htmlentities($_SERVER["QUERY_STRING"], ENT_QUOTES):""); ?>"