The results page should have the Search server behavior listed in the server behaviors panel.
To do it manually replace this code:
//keyword array declarations
//comparison list additions
$WADbSearch1->addComparisonFromEdit("surname","surname","AND","includes",0);
$WADbSearch1->addComparisonFromEdit("postcode","postcode","OR","includes",0);
with this:
//keyword array declarations
$KeyArr1 = array("forename", "surname");
//comparison list additions
$WADbSearch1->keywordComparison($KeyArr1,"".((isset($_POST["surname"]))?$_POST["surname"]:"") ."","AND","Includes",",%20","%20","%22","%22",0);
$WADbSearch1->addComparisonFromEdit("postcode","postcode","OR","includes",0);