Citroen AX - idle speed

[LondonHawk]

Hi all, I hope you can help.
I have an 89/90 Citroen AX 1.1 (manual choke) It runs fine most of the time, but with the cold weather I'm finding that the idle speed tends to be all over the place.
After about 5 mins, the idle speed will go bananas. For a while I assumed it was my choke control but if I pull the choke out a long way, the engine will overrev. As I push the choke in again, it'll stall. [:(!] I'm either coasting into traffic lights and stalling, or coasting into traffic lights and the engine is revving like crazy. After about another 15 minutes it will behave itself again, and I can pootle on my way without having to try to hit all the pedals and buttons at the same time [:D]
I've read some posts on here regarding the idle control valve (but have no idea what this means), so I think it may be quite a common problem.
My car knowledge is pretty much limited to where the fuel, oil and water goes, so any help would be much appreciated.