The Council are advising us that the DBS service write to you and offer you the update service (£13 a year as opposed to £60 every 3 years). This is not the case, or at least I can never find it and missed it last time. In order to join the update service, you have to do it yourself the moment you get your application reference, or when you get your CRB certificate.
In order to join the update service go to https://www.gov.uk/dbs-update-service and follow the instructions – make sure you have your certificate with you. 🙂