Here, courtesy of the green folk at Nigel's Eco Store, are some examples of solar powered shed lighting from Solar Mate. Here's the info:
"The Solar Mate solar powered lighting kits address the problem of illuminating areas where there's no mains power, and can be easily and safely installed by anyone (and is also exempt from Part P of the Building regulations). Using purely the energy of the sun, Solar Mate’s solar panel will collect enough energy during the course of a day (even in Britain) to power its bulb for between 5 and 7 hours every day of the year (5 hours in the winter – 7 hours for the rest for the year). Solar Mate has a 10 year warranty so will easily pay back its investment many times. There are 3 solar mate kits so you can light small areas such as sheds or larger areas such as outbuildings, stables etc. The smallest kit at £17.99 lights smaller areas such as sheds and summer houses and covers 16 square meters."