Functional Hearing Assessment
Unless things have changed recently, following refusal of Class 1 certification you should receive a letter from the Aeromedical Dept. requesting a "Functional Hearing Assessment", after which your Class 1 will have the limitation "SSLFHA - Special restriction as specified :- Functional Hearing Assessment Required within 3 months of renewal/revalidation medical"
See CAA application form SRG1205 issue 3 for details, which should be completed by a Training Captain or CFI.
A quick trip in a C152 with a local CFI will do the trick!
Hope this helps.