Thanks folks...I've already purchased a Berker twin usb which fits the blank -off ebay. I stupidly thought it would be dead easy to splice into a 12v wire at the back of the drawers. Unfortunately my electrician friend says it's not that simple ...something to do with the negative running into the light fittings? I should have discussed this with him before purchase. Going directly to the Sergent fuse box was the other option but without a proper wiring diagram this could not be done. Perhaps I'll just stick the phone charger back in the 240v socket like I did before!