Right now, based on your link, I am assuming you want to access a web sevice via REST from another site. As you may already know, there are now WSDL for REST and neither is there a common interface. I would suggest straight up php SimpleXML to interact with the XML?
The key thing here is that you would have to work with the structure of the xml document.
$uri = '[url="http://pcls1.craftyclicks.co.uk/xml/rapidaddress?postcode=rm81dl&response=data_formatted&lines=3&key=d476d-d308a-f12d9-00427"]http://pcls1.craftyclicks.co.uk/xml/rapidaddress?postcode=rm81dl&response=data_formatted&lines=3&key=d476d-d308a-f12d9-00427[/url]';
$crafty = new SimpleXMLElement($uri, NULL, true);
$array = $crafty->xpath(/xpath/query/to/access/node);
foreach ($array as $delivery)
{
// do what you gotta do here
}