Sorry to disappoint but the issue is that on a lot of the aircraft, especially the 747, the number selected doesn't accurately relate to the temperature in the cabin! Being told to select a particular temperature, rather then using sensible judgements, could end up with the opposite effect.

Have quite often had the temperature set to 20 or lower down the back of the 747 only to have someone not working there shove it back up to 23. I really don't think this memo to all crew will make any difference at all, if u feel it's too hot or cold I'm afraid you will still need to make ur views known to the crew.

On a typical 747 flight I will probably need to adjust the temperature 2 or 3 times during the course of the flight to keep the WT cabins cool. The 747 also has a bad habit of resetting all cabins to 25 degrees at various times, requiring a quick run to the front to start cooling things down again.

If you fly with me, it'll always be cooler, I'm Scottish and cant cope if it's too hot!