I was invited to join my GP's PPG a few years ago. I think the GPs were paid a bonus for setting them up. I found it was undemocratic, as the GP appointed a friend as chair, we were not given any indication of the remit, all members of group were selected by GP, so some members became rather full of their own importance. Some Wanted to sanction people for missed appointments by a 'three strikes and you are out' sort of approach. They were totally oblivious to the notion that there could be a valid reason (e.g mental health problems, dementia etc) for patients missing appointments, and did not want to consider that when I mentioned it. Another thing I mentioned was the PPG invited members were, apart from me, all male and beyond retirement age. Not a representative group at all. The reason given when I queried it was that 'people who are working during the day can't get here'. They were dumbfounded when I suggested evening and weekend meetings.
I believe more recently, where I live at least, the PPG s are feeding into the larger local Clinical Commissioning Group, which decides how NHS funding is spent. As funds have to be spread thinly, it can have a bias towards issues of those making the decisions.
All this leads me to conclude that being involved in a PPG, is important, but be prepared to be bogged down by people with an agenda of self importance, and be tough and resilient, and prepared to be shot down in flames if your ideas go against the majority.