Bought a £6 lamp from CPC. Cut the mains plug off it, spliced down the brown and blue cables within and added clips to them.
Put in a 2W LED bulb and voila - you have a battery powered lamp. That £10 7Ah battery will run this 12V light for about 30 hours. Our typical 100Ah batteries will run it for 500 hours.
And it is bright!