The CAA has not gotten around to creating a specific DRONE Pilot Radio License. So although you will be using only a portion of the information in the Restricted Radio License, you take the same exam as Private Pilots, and will be issued with the same radio license as Private Pilots, (And NPLs, LSA, Glider and Balloon Pilots).
This means you will have to learn the same stuff for Radio the a PPL and LSA pilot has to learn, as well as the Drone-Specific flight plan. This Course covers everything you need to know to pass the verbal and written Restricted Radio Exams including Drone specific Flight Plans and Radio Work.