This information is not collected centrally.
We have no evidence that there are widespread failings in data handling that would warrant the burden of a new data collection. Errors in data handling might include wrongly addressed e-mails, conversations in public spaces and other errors which need to be managed locally.
Responsibility for handling data securely and confidentially rests with individual local organisations. If a patient has any concerns over how errors to medical records are handled or finds they are the subject of a confidentiality breach they should report it as soon as possible to the organisation concerned through their complaints procedure process. In extreme cases incidents should be reported to the Information Commissioner.