NSW Lifelink; better message reported when the Lifelink website is unavailable

When the NSW Lifelink website is unavailable it returns an HTML response rather than an XML response. This results in a message stating that "The response received was not a valid XML document." and includes "The character '>' was expected".

This is now handled better, resulting in a more user friendly message stating that the response received was, for example, Status 503 Service Unavailable, and to check the EDI Transaction's Response for more detail.