Don't know if it's such a bad thing necessarily to change instructors mid-PPL - I did just as things were getting stale and I was doing circuit after circuit, and the change of perspective really shook me out of the rut. So perhaps it's not the end of the world if you do make a bad decision (or have one made for you). That said, it took a little bit of expensive airbourne time to change to the new bloke's ideas on how it's done. . .. .But how are you supposed to know except in hindsight whether your first instructor is any good? I don't think you can. What you're looking for, I suppose, is someone who really takes you on as a project.. .. .I reckon a nice friendly club is nearly as important as the actual instructor - maybe one will lead to the other.