A recent survey showed some of the databases aren't as compliants with DEFRA rules as they should be. There is a bewildering array of them out there holding data and they need to tell you who to ring if they don't hold your pets details.
There are also real concerns over being registered on multiple databases, which is happening. The problem being that if you aren't carefull your pet can end up with an out of date entry at an old address. The safest is a single entry.
The current list is:
Animal Tracker, Chipworks, Identibase, MicroChip Central, MicroDogID, National Veterinary Data Service, Pet Identity UK, Petlog, ProtectedPet, Smartchip UK, PETtrac
We recommend Petlog