I had a Bosch single oven with a stuck glass bulb cover. The glass cover was after using considerable force to unsrew it (anti clockwise) just turning round and round without engaging the threads, I suspected (rightly as it turned out) that the whole fitting was turning round in its housing with susequent stripping off of the electrical leads. Solution. Switch off cooker electrical supply, unscrew the two retaining screws which attach the cooker body to the base unit (found at the top corners when door is opened) ease the oven forward about a foot (30cm) - support oven on pile of books or similar, then remove the two retaining screws which hold the metal top cover sheet in place ( star headed srews), lift off metal cover, with a screwdriver or similar,after removing the old bulb, wedge it through the holes in the top of the exposed metal part of the light fitting hold it firrmly, then with the other hand turn the glass cover anticlockwise, it will release fairly easily. Clean cover with pan scrubber and or sand paper making sure the threads are clean, If the electic leads have been pulled off or broken, re- attach spade connectors or fit new ones (Maplins or similar) the earth is the green wire at the connector on its own.( with earth at the bottom, brown and white go to the left hand side and red and white to the right. Fit new bulb 40W ( Maplins £2.69p or Wilkinsons 25W £2.04p.) Screw back glass cover making sure NOT to tighten all the way. Refix metal cover, push oven back, fix retaining screws and switch on oven. Total time if you have the bulb and spade connectors to hand about twenty minutes. It does work.
Peter persistant, February 2010