These are fair enough answers. The point I was hoping to make was that when we board the aircraft, eat our meals etc etc the temperature seems to be ok (to me). It is only when we have been packed off to sleep that I notice the rise in temperature. Generally I am not the only one.
So, I can see that the temperature throughout the cabin may vary depending on where an individual may be seated and of course their own personal view of what is a comfortable temperature or not. But given that the aircraft is an insulated and isolated cylinder, I might have presumed that once the overall cabin temperature was 'set' it would stay reasonably constant even if different zones of the aircraft are at different temperatures. I think safelife's suggested answer is likely to be correct. But I would be interested in any responses from cabin crew. (i'm assuming safe life isn't).