DVLA Number Plates generally refer to car registrations that have not been assigned to a vehicle yet. These registrations are held by the DVLA Swansea until they are purchased - at which point the buyer becomes legally responsible for that registration.
DVLA Plates include the Prefix range of registrations and the current format plates. The most popular format is the prefix range as these plates can be assigned to more vehicles (DVLA Plates are age restricted) and are generally cheaper in comparison to other ranges.
Firstly, if your vehicle is a prefix registered car you'll need to purchase a number plate from the prefix range - current format plates are for newer vehicles. You'll have to choose a prefix plate starting with either the same letter as your current registration or a letter coming sooner in the alphabet. For example, if your car was first registered on a 'H' prefix plate, you'll need to purchase a prefix plate between 'A' and 'H'.
If you vehicle was first registered on a current style plate, you are free to purchase any prefix plate you wish. If choosing another registration from the current style range you'll need to ensure the plate chosen is from either an older range or the same range as your car currently features. For example, a '53' vehicle would need to display a prefix plate, or a current style plate from the following group: '51','02','52','03' or '53'
Actually, yes. There is a free downloable PDF which lists all the dates relating to UK number plate releases. You can grab the latest copy of it here: UK Number Plate Release Dates
New DVLA Number Plates are released each year. In 2010 the upcoming releases are: