I am also an assessing clinician with a charitable organisation called BAPAM (British Association for Performance Arts Medicine). They have previously offered to pay me a fee for any clinics run, which I have always waivered. Instead, voluntary involvement has helped offer me insight into how this charitable organisation is run. I have also been transparent to my medico-legal defence organisation about my involvement with BAPAM.
I am on occasion, an assessing clinician with BAPAM (British Association for Performance Arts Medicine). For this I do not collect a fee, but relish the insight into how this charitable organisation is run.