In Germany, pilots doing the initial call on the approach freq, should report only the current ATIS letter. Even if the QNH is stated by the pilot, ATC will combine the first clearance to an altitude again with the QNH.
My question: When will the pilot switch the Altimeter from Standard to QNH?
With the first clearance to an Altitute, or when passing the Transition Level. I know it should be the last, but the first seems to be more practicable.