Pull out the metal strip at the top of the oven. This gives you access to a metal panel on the top of the oven's body, which is held in place with two Torx T20 screws. Space above the oven is restricted, but you can undo them with a T20 bit from a universal screwdriver set. Mine were not done up tight. You can then lift out the metal panel, and reach inside to unscrew the lamp. Mine was a 240V 40W SES oven lamp rated to 300ºC.
James Gilbert, September 2008