I am sure there are other good schools too, I am not proclaiming Stapelford is the best, however from what I have experienced they seem to run a pretty clean machine. And if they are busy, well that shows a few things, many students, they don't need to drain your pocket for money, because they need to free up space for the next student.
I have seen many schools/instructors maybe less busy, but this also means they will depend more on your business, and for you to stay their student longest possible.
No place will be perfect, everyone will have their positive and negative stories, I personally like the places that do not oversell their establishment, and give me peace to make up my own mind and then decide, there are many slick sales people, and to be honest they love you, and make you feel they are your best friend, until you have handed over your money, and you dont exist anymore!
Also personally I would want the training to be rather harder then the real test, and the instructors to be more strict then maybe required for the CAA exams, I personally would not like to get an easy ride just because I might feel to sensitive.
I have heard many stories of some pretty awfull PPL students & PPL pilots, flying at both Stapelford and other flying schools - and maybe some of these do deserve a rough ride, so they either wake up and get their act together, or if not possible to adhere with good airmanship quit flying completly.
I also believe it depends on each students attitude, when I started I did not go asking them for advice, and what to do, I knew what I wanted, I got one instructor, I was happy with him, and agreed directly with him that I did not want to swap around with instructors, and planned all my bookings directly with him, and guess what? I did every lesson with him, sure there was frustrations due to weather conditions, runway conditions etc., however considering the price and their reputation is pretty good, you can't go to much wrong.
I am sure there are other equally good around, which might have similar prices, and there are others that cost much more.
What I liked was the honesty that they did not try to rip me of by making me fly more hours then I needed, when they felt I was good enough, they let me have my skill test, and to be honest, at much less hours then I expected. I had not been flying for 16 - 17 years, and I had 14 hours dual before my skill test, I actually wanted to fly a little more, but was not required.
Would I want to pay another extra 30.000 - 40.000 (Oxford example) for someone to hold my hand, a place like Stapelford it's up to yourself and what you make out of it. For some, this is not always the best.