Display screen gone blank, but mobile still switches on/off etc, with noises etc, just no graphics. Can anyone tell me how to fix it?

You'll have to go to the place you bought it and have it repaired, or more likely, replaced, and if the screen is broken or not working, if you have a warranty and didn't get it wet or damage it, then they should cover it, or if not, You'll probably have to buy a new phone. The screen will probably have to be replaced and that's probably more expensive than just buying a new phone, and if you open the phone, I'm willing to bet that not only will it be impossible to fix, but any warranty you have will be voided.