All of your information is kept in accordance with the Records Management Code of Practice for Health and Social Care 2016. This is available from - https://digital.nhs.uk/article/1202/Records-Management-Code-of-Practice-for-Health-and-Social-Care-2016
In general terms, medical information is retained for at least 10 years after treatment; or for children until they reach at least 25years old. There are exceptions to this. Any enquiries should be made directly to the Data Protection Officer.