When my S1 was nearly new it went to Trimoco, Dunstable for poor cold starting. They were the No 1 Rs Dealer at the time and they contacted Ford who said to disconnect the cold start valve. The instructions then passed to me were to cold start the car with the throttle peddle depressed about half way. Started really well for the next 25 years until we parted company. Sad day.

Try it it might help.
Cheers, John