Cold start idle

When is cold the engine sit on idle on 800 rpm , what should be the problem?
In past idle was on 1100 rpm.
 
I'm wondering if it relates to lower than normal battery charge or something... I've seen an increasing number of people asking the same question.

Mine used to cold start as normal at around 1100 revs when I got it a year ago, it no longer does this after being stood for 24+ hours. However if I go for a drive and come back to it once it's cooled off again it starts up well and revs straight to 1100~rpm.

Also I've had it remapped in between and it made no difference so doesn't relate to the map.
 
There have been mornings where it's close to 0 degrees and the Clio idles at 800 and others where it's 17 degrees and it idles at 1100. I personally wouldn't worry about it.
 
Thx for answers guys !

DS197 . it happenend to me same things , sometimes when outside is 10 degrees the rpm are at 1100 , when outside is 0 start at 800...

in this morning was 0 and start at 1100 but yesterday i run the car in high rpm a little . I use the car daily and the distance from home to work is 4.5km so the engine is not complet warmed.
I will replace the thermostat and if i see any change i will post here.