Samotnik, lets look at your theory.
If a aircraft is given a descent from FL170 to 8000 feet QNH 1005. Both pilots set QNH and announce it following whatever your company SOP's are.
For some reason they stop at 11000 feet on the QNH.
Now if they instigate this they will contact ATC and tell them that they have stopped at 11000 feet.
If ATC have stopped them they will tell them to stop at FL110 or 11000 feet.
Either way ATC will immediately be in the loop as will any other aircraft in the vicinity.
I have no idea what your company SOP's are about transitioning to and from flight levels, but the Three companies I have been in all have the same rule, When you are given your first flight level by ATC you set standard and when you are given your first Altitude you set QNH. I was also taught this when I did my IR.
This way you never have any problems and yes, I find this works all over Europe and even in non radar controlled Africa, which I have had the pleasure of flying in.
It is only a problem if you make it so.
