Ah am making some progress.
Nagios3 is installed and I have got the login screen to come up, but just 1 quick question,
Because of the way I have installed nagios it has not installed to the default directories as in the ubuntu TUT. My install is in /etc/nagios3 etc etc.
Can I substitute the following from the quick instal guide:
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin with
htpasswd -c /etc/nagios3/htpasswd.users nagiosadmin
Just checking, because I think this is the only bit which is stopping nagios from loading, because I haven't set ht access