Planning approval for an Annexe will depend upon whether planners view the converted out building or extension to be part of the main house or the impression is given that the Annexe could easily be sepaated off into an independent dwelling.  Some local authorities can be quite sensitive to allow approval for Annexe's, they may request that there is an interconnecting door, that the Annexe doesn't have its own kitchen or they may include a Condition in the planning approval that states the Annexe must only be used for ancillary purposes to the house.


Further investigation should be made to your local authority Council Tax department if a member of the family is using the Annexe full time, although you may be allowed discounts depending upon the occupier.