Turn the electric supply to the lights off, remove the tube, (the end caps are spring loaded) then remove the 2 screws that secure the cover. You'll see the electrical connection inside - a live, an earth, and a neutral. Disconnect these. You should also see the screws that hold the lamp unit onto the ceiling - undo them and the complete lamp unit will come clear. You can then install a ceiling rose which will allow the fitting of a usual bulb.
John
May 2008