thanks for the reply Ray
I have Mail, Net_SMTP, Net_Socket and Auth_SASL installed, (the other packages install by default on godaddy anyway).
I checked the server, the files seem to be there. the problem stems from line 349
$this->_smtp = &new Net_SMTP($this->host,
I checked the file locations compared to another host I use - just the same.
So I changed the file path in smtp.php on line 348 from relative to absolute
This gave me a different error about being unable to find Socket.php
So in SMTP.php I changed the path on line 22
This then reloads the page without errors. (and adds an entry to the email log), so all i had to do next was configure the port and username settings.
Success !! - but I won't be recommending godaddy as a host ;-(