Hey Falko, thanks for the /etc/X11/xorg.conf reference - I've had a look at this file on another working installation. This is encouraging: looking at the file I can see that there is an entry for the monitor being used and for the graphics card.
So what I intend to do is manually change this on my problem installation to use the IIyama CRT and then restart. I will have to find the standard name string for the monitor - I know I can't just put in any old string.
Do you know where the devices referred to in this file are defined? Like a kind of master standard list? I'll do a search on the internet.
The advantage with Debian is that there are no variations of it. By this I mean by comparison Ubuntu is available in Desktop and Server versions - the Debian distribution is just one offering, containing both server and desktop programs. Sure there are Debian versions, e.g. 3, 4 etc. but there are no variants.
I tried Ubuntu server but there is no GUI as standard. I would like Ubuntu Desktop + Ubuntu Server all in one install. Looking at the official Ubuntu forums and support pages there were several ways to get the functionality of both but there ought to be a single official standard way.
I'll definitely let you know how I get on with details of changing the xorg.cong file - whether it works or not.