Despite replies from Sony support site, (do the @#$% obvious ) I gave up on trying to get my keyboard going again.
I went through a Control Panel / Recovery with the Windows disc.
Went smoothly, and keyboard works again. No Fn Keys.
One thing I learned was Windows Key + X gives the functions I was missing with the Fn key, so laptop is usable.
However, Milo said one should always upload the latest drivers. I had used the site he pointed to, and there is no doubt. The W7 Launcher driver runs but then says it is for Vista.
I get the feeling Sony have dropped the ball on this one, and just left my VGN-NR498E out in the cold. If there's anything I have missed, I'd love to know. I'd like to experiment before doing all the updates and loading Office again.