Лучше всего отделить ваш запрос cURL от цикла ...
так что-то вроде этого подойдет ..
while($dataR = mysql_fetch_array($data)){
$postcode = str_replace(" ", "+", $dataR['Postcode']);
echo $postcode."<br />";
$oPostcode = $dataR['Postcode'];
// Retrieve the DOM from a given URL
$url = 'http://www.1.com';
$fields = array(
'txtPostCode'=>urlencode($oPostcode)
);
//url-ify the data for the POST
foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; }
rtrim($fields_string,'&');
// Execute youru cURL here.
$data = array(
'url' => $url,
'fiels' => count($fields),
'field_string' => $fields_string
);
executecURL($data);
$html = str_get_html($result);
print_r($html);
}
function executecURL($data) {
$ch = curl_init();
//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL,$data['url']);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch,CURLOPT_POST,count($data['fields']));
curl_setopt($ch,CURLOPT_POSTFIELDS,$data['fields_string']);
//execute post
$result = curl_exec($ch);
curl_close($ch);
unset($ch);
//close connection
}