It could be that the light housing has to be removed. I found this for the 1999 models ---- "You need to unscrew the screw at the top of the rear light array (Philips-type screwdriver). This loosens the light array at the top, just enough for you to get your fingers behind it. Lower down, there are two lugs which secure the bottom of the light array. With a bit of jiggling the lugs will disengage, releasing the whole array - during this process, it feels as though the lugs are going to snap off!! Once the light array is in your hands, just twist the plastic holder of the bulb you want to change anticlockwise, remove the bulb (same fitting as a bayonet domestic bulb) and reverse the process to re-install. "
Thank you very much !