OK, in the absence of complete information, I am proceeding by trial and error.
I deinstalled the current install, and started over again.
I tried leaving the hostname and domain name blank during setup.
You cannot do this as it won't let you go forwards in the install script.
I tried leaving the hostname blank and adding my ip address as the domain name.
This works, but it sets up an A record to www.yourip
which is not want we want at all is it !!??
So I deinstalled again and will try installing again with different variables until I crack it......
I swear I will write a decent setup howto for a fix ip address site after all this torture is over.