Huh? The door locks with the central locking system. When you want to open the fuel door, you just push on the front (closest to the passenger door) side of the fuel door, and it opens. No need for gimcrackery.
Japanese cars use the much more complicated system with a remote switch to overcome the locking system. Our MB's lock the fuel door tight (sweet little dead-bolt, very trick) but eliminate the need for a remote release by hinging the door on a fulcrum so it swings open with a slight push.
1998 C230 "Black Betty"