If you have a current UK EASA PPL then you will have a UK FRTOL built into it see Section XII Radiotelephony Privileges.
The UK FRTOL makes no distinction between VFR and IFR; how can the flight conditions determine your ability to communicate on a radio?
The IFR Comms paper is an EASA written examination and is not administered by RTF Examiners. It should be incorporated in the IR written exams.