Well thankyou for the highly detailed advice !
Unfortunately though my new monitor has just died so until it gets replaced I'll not be able to try out your solutions as I don't want to set up my X-server to use with my old monitor (again) as I've have enough trouble with X for the time being (why all Linux GUIs don't have GNOMEs ability to choose the desired monitor size and resolution from the list of options supported by the device, rather than the "use the X-Servers maximum capabilities, one size fits all approach" is beyond me)
But I shall bookmark this article and will get straight to it later in the week (a replacement monitor is being delivered thursday)
So thankyou very much once again for the info. It was most helpful and looks guaranteed to work !