Altimeter Setting, Transition

[scud]

Hello,

This question is for anybody other than North Americans (no discrimination intended).

You're outside North America, and you're cruising at FL260, approaching your destination airport, and you're talking to Terminal control.

The controller says that "you're cleared to descend to 6000 feet, QNH 1015".

Published transition is FL090.

Do you reset your altimeter to QNH:

1. As you're reaching the transition layer, or

2. As you're leaving your cruise altitude of FL260?

For anyone answering 2, is there anything specifically in the applicable country's AIP or in your company's flight operations manual that prescribes this?

Thanks,

Scud