Thanks for the link.
In the meantime I managed to use FAR to reinstall the FS (see http://forums.se-nse.net/index.php?showtopic=7480) and then used XS++ to customize. When I turned on the phone it was OK.
If I did another master reset "delete all settings" then I got the problem back again, no LEFT/RIGHT softkey, softkey legend area close to the top of screen rather than at the bottom. I repeated the FAR/XS++ technique and it was OK again.
I was about to sell the phone so I will stop there and not attempt brown to red in case I really break it! I can now walk into the shop and sell it as working.
Thanks
Darren