The Prof is spot on. When I got my PPL in the 1980's as an experienced helicopter pilot I just had to do 12 hours and a check flight. I was then licenced to fly with a passenger for a year and could validate my PPL merely by flying 5 hours per year. There are a lot of very inexperienced PPL's out there.
Further to the Prof's list you can not fly with a passenger unless you are qualified to do so. The following is an extract from the BGA's rules: Before carrying a club member in a glider, the pilot in charge must be authorised by his CFI and hold a Bronze badge or higher certificate and have at least 50 hours P1 on gliders. To give trial lessons, the pilot must have a Basic Instructor rating or higher instructor rating. The pilot must be in current practice, be familiar with the type of glider and method of launch.