https://www.caa.co.uk/general-aviation/pilot-licences/applications/conversion-of-an-easa-flight-crew-licence-to-a-uk-part-equivalent-licence-1/
Conversion of an EASA flight crew licence to a UK part equivalent licence | UK Civil Aviation...
Information for previous UK licence holders and holders of EASA licences issued before 31 December 2020 (updated January 2023)
flight crew licencecivil aviationconversioneasauk