Not idling when cold

Pretty much what the thread title is saying, my Mk2 RS isn't idling when cold. If I don't have my foot on throttle or the car in gear moving that car will stall. Once the the engine is warmed up its not a real issue. I'm suspecting that its a problem with the choke as the choke barely works and the weather has been bitterly cold.
 
I'm not suspecting plugs or leads as the engine isn't miss-firing. Outside of the choke I also have suspicions for tuning or timing causing the problem. The biggest problem for me, adjusting the choke, tuning, and timing is all out of my current abilities and being a full-time student I can't exactly afford to go to a shop to get it looked at.

I'm running a standard pre-ADR Weber, its the only standard part of the engine.
 
It's also now confirmed for doing it when at normal engine temp, just drove from Adelaide to Mt Barker, went to stop at the lights and engine stalled, when it did idle it was at around 500rpm while it had been idling during the day at around 900-1000rpm. I also noticed that when accelerating from low-rpm the engine response isn't quite as sharp as it had been in the past.
 
For richening the which way does the screw have to be turned? The Gregorys Escort Workshop Manual doesn't say a damn thing adjusting the mixture.