I agree that you should report someone you know to be doing illegal charter work but unless the CAA have the will to do something about it, nothing will get done.
I have been at events where PPL's have flown "friends" in and also where CPL,s have appeared to be doing charter work without an AOC.
Without concrete proof what can you report to the CAA, just heresay and rumour.
This is upto the CAA to police not us.
Jarvy