This may vary from country to country, but I always understood that here in BE the (EASA compliant) PPL automatically includes the radio license. So that only people flying the various Annex 2 types need to take a separate radio exam - as I did. Is it different in UK?
As I understand it is different in the UK who filed a difference that you have to pass a practical RT exam (as well as the theoretical) to qualify for the RT licence.