Hi Graham,
You could also try emailing William-Bell to see if you can get hold of the book and software, or maybe just the software if they have run out of the books.
http://willbell.com/contact.htm
The other thing to watch out for is if you find a copy to make sure it is version 2. William-Bell used to offer an upgrade from v1 to v2, but I’m not sure if that is still available.
Andy