At the risk of kicking things off which is not my intention. I might add its been years since I have been involved with flying school politics or even know what's happening in Scotland or the current bunch of characters.
I have run the ops desk in my past and have been accused of having a golden bollocks special FI.
The fact is he wasn't, he was just there when ever he was needed. He was hungry for the hours. The punters liked him and he put the effort in to the trial flights and turned them into PPL's. Never needed to be told to get the aircraft out and get them fuelled it was just done. Punter walked in the door early doors and you turned round and he was their plane ready and itching to go.
If you got that feeling which we all know that the punter was a good to convert yes I would stick them with him or do it myself because that was the best way of getting a PPL course out of them.
What some FI's don't get to hear is the punters that ask for change of instructor or wangle things so they come in on certain peoples days off. Then ask to be kept with a different one as it there right as they are paying hard earned cash to learn to fly.
So I agree there may very well be some unfairness but to be honest its usually in my experience been because certain FI's need to have a good look in the mirror and sort their own **** out.
Its usually those FI's that are going to multiple escape party's of FI's who are less experienced than themselves and have been in the game for a shorter period.
Now I am not saying this is either fair or applies to everyone or every school. But from what I saw it holds true alot of the time.