I'm not ready to throw the phone at the wall yet, Kenny, but thanks for the suggestion.
Having googled this I still haven't come up with an answer (the so called manual is a very small booklet which covers only the basics). One comment I read said that any key would light the screen again at the place where it went dark. True, it does but then the symbol on that key is also on screen.
As for the backlighting, no-one seems to know how to keep the screen lit up for longer than 12-15 seconds. This is such a great little phone except for these two niggles.
Anyone else got any answers?