Sorry Duncan but how do you check the internal temperature while it is in standby mode? You need to awake it to see any readout on the display.
We have already established from the HFN report that there is no change to power consumption whether full on or in standby. That can also be used as a simile for temperature i.e. the mean temperature could only decrease if power consumption decreases too ( NB: there are always minor fluctuations due to variations in ambient temperature) .
If you have a separate dCS clock with that little thermometer icon indicating stable temperature you will see that it is normally immediately displayed when recovering from standby ( sleep). If the internal temperature did drop the recovery time would not be instantaneous.
In any case: