If an organisation is being difficult about giving you your data following a formal request called a Subject Access Request SAR you can ask advice from the Information Commissioners Office ICO. The helpline team are excellent and will give sound advice and if necessary recommend action.
I am posting this as a member has had difficulty obtaining copies of medical records from a GP Practice following an SAR. It is not permissible for GP Practices or any organisation to summarise the information you have requested or withhold information. Third party data will be redacted but you are entitled to all information that relates to you. This is a legal requirement and if it not complied with organisations can be fined by the ICO