You have two options you can choose from in order to maintain your personalised/cherished number plate. The first option is to transfer this number plate to another vehicle, and your second option is to keep the number plate on retention until you have another car to put it on.
To remove your personal number plate, contact the DVLA by calling 0300 790 6802 or visit the DVLA website. They will provide you with a new registration number, which you should attach to your Mercedes-Benz prior to collection. This will enable you to retain your cherished plate and avoid having it sold with the car. Please bear in mind that this process can take the DVLA up to eight weeks to complete, so you need to contact them in good time prior to collection.