Unfortunately it is out of warranty. Are you saying that you do have to twist/unscrew the lens to get at the bulb? Just want to confirm in case there is something else I should be doing instead.
I am having exactly the same symptoms with my Neff double oven in that it trips out the main RCD every 10 mins or so if the fan oven temp is set much above 180c.
Has anybody got any ideas on where the problem might lie.
The model is U1320B0GB.