When the CAA operated the Microfiche system, everything including scans of all past paper communications you had ever had with them in relation to a licence or medical was contained on that fiche. About 16 years ago the microfiche data was migrated into electronic (pdf) format and is now held in a large electronic pot. In theory they still have everything however; in the early stages of migration some of the tagging was not that good and I have heard that not everything comes out when they search.
If you ask for a copy of your records they are obliged to supply them.