Finally found the fault (well almost). I fiddled with the wires underneath the ignition key switch and the lights came on. I could then start the bike as normal. There's a loose connection (as uzi_999 mentioned) amongst those wires. I'll take a good look at the weekend when I have more time.
Thanks for all your help.
I have a YBR125 (year 2006) which wont start. I turn the key and and no lights turn on. Im sure the headlight and neutral light used to come on (I have checked it is in neutral!). I have charged up the existing battery and even tryed a brand new one now but no luck. There must be a loose connection somewhere. Any suggestions? Please help.