The Retention Scheme enables a number to be held apart from the vehicle it has been assigned to, for a 12 month period pending its re-assignment to another vehicle. Only the registered keeper of a vehicle is entitled to apply for a right of retention. Application form V778/1 Retention of Vehicle Registration Mark must be completed and the application fee is £25 plus an assignment fee of £80, bringing the total payable to £105 (at time of publication). Successful applicants are issued with a V778 Retention Document, valid for 12 months, which records details of the registration number, the grantee (the applicant), and nominee details where supplied in the application. If, after you have received your document, you wish to add or change nominee details, you will need to apply to DVLA, returning your document together with a fee of £25.
http://www.regtransfe.../retention_scheme.asp