DTP
You're giving the CAA less credit than they're due on this one. I asked for permission back in my PPL days because I didn't have the 200 hours, and had a very pleasant conversation with an ops guy from the CAA where he outlined what would be acceptable, and it was quite cautious - no off airfield stuff. I'm not saying everyone would get that condition applied, but he clearly felt that was an appropriate restriction for my level of experience at the time.
When the permission came through, one of the conditions was that the passengers were to be made absolutely clear that the flight was not a public transport flight, that effectively they were afforded only the same protections as friends of the pilot would be, rather than that of an AOC.
Now of course it's going to be up to the pilot exactly how he broaches this subject, but I would have thought that anyone who had the decency to offer a charity flight, then the honesty and openness to ask the CAA and get permission, would probably have the good sense to follow their instructions and make this clear.
As long as everyone knows what they're getting into, I can't see there's a problem.