There should be no reason why a number of different inst's should make a difference. A good FTO should provide standardisation for all the instructor chappies.
I might also add that diiferent instructors can add a little "flavour"
I have been instructing for a few years now and when discussing another lesson with a fellow instructor, he/she might mention a method or reminder that I didn't know or vice versa.
There are as many methods as instructors, a little exposure towards the middle part of the course to different approaches of different instructors cant be bad can it?
If you are worried then speak to somebody a little more senior and see if you can get booked with the same chap/chapess for a muber of consecutive lessons if you are worried.
