Two steps forward, one step backwards: happily for all concerned, Fedora works fine at the 1600x1200 resolution it defaulted to when I restored the 'generic VESA' driver. It is in fact fully usable.
However, I was interested in getting the full 1920x1200 resolution out of my wide-aspect LCD panel. Some guides on linux-laptop.net are very helpful regarding many areas of the Inspiron 8600, and some of them suggest adding particular modelines to XF86Config to enable the higher res.
I've added them, but once in KDE I don't seem to be able to select the mode I have created. There is a tool called something like 'Display configuration' where I can choose from various resoultions and colour depths, but the mode I've added to the config file doesn't seem to be showing up in the list. Should it be? If not, how do I select it?
A thought: do I need to set up a specific driver for my graphics card (ATI mobility radeon 9600 pro turbo) before I can use the custom resolution?