In my experience of 9 years, and having done PPL training, IMCR, Night qualification, and renewals of JAR and FAA licenses with a few different airfield organisations in South East UK, I would disagree with Jan and Rod1. Thats not to say its not their experience, but it isnt mine.
The problem is though, that as a PPL sometimes you are at home, on the train, whatever, and you arent in talking distance of your instructor. You could try him or her on the phone, but either they are flying / with another student, or for longer questions, they might need to charge you the clubs going rate. Therefore it is easier to test and gain understanding from a variety of sources, including on here. Of course the advice cannot be taken as gospel, even from a qualified instructor, as he is not your instructor, delivering your schools syllabus. But its fine to ask, and improve your knowledge anyhow.
The other problem is that most schools or communities have little time or resource to deal with post-PPL subjects (e.g. going somewhere more than 45 minutes away, information on the specifics of a certain airfield, or operation like filing a flight plan or a GAR), or even the most basic like how to use the GPS or even what tablet naviation application they recommend). Most of that is beyond what the schoool exists to provide, but if you are at a good school, then beyond the helpful people here, there will be local pilots who will give you their 'advice' for free.
On forums like this, you can be inspired by what other people have done and begin to think beyond your basic PPL and see what other opportunities exist. After my PPL, I found Peter's trip reports incredibly inspiring -
Peter's Trip Reports