I've sussed the wristbands!!
Just came back from the London Gig, been tampering with the wristbands and know how to get them working again!!
Take all the screws out the back of the plastic box, test the battery and contact by sqeezeing it together, it should come on when u sqeeze it. Put the back back on the box but don't tighten the screws down fully, keep sqeezing it as ur doing this to check it still lights up. U should get to a point where the screws are tight enuff to hold the back on but loose euff to for the box to act as a button so u can maunally operate the light!
Job done!! Keep on Coldplaying!!