SO - You are inputting 2048x1152 to a monitor that is display-capable of only 1920x1200 - and you wonder why it doesnt show part of the display ? Go to 1920x1200 on the laptop and you will see the whole display. IF 1920 is not good enough, you will need to go "back" to the 2048- capable monitor.
No I was putting 1920x1200 into the monitor from the laptop, so all should have been well. I eventually solved this issue by doing a 'reset' on the monitor.
As I was using the analog input it just neede to rescale.
I was just suprised that an out of the box, new monitor was so badly set up at the factory that it needed a full reset.