I noticed quite a loud noise the other day, just after starting the car and it disappeared when I floored the clutch pedal. The car had just had a new cambelt so I was concerned that something was amiss. I went back to the dealership (10 miles) and by the time I got there the noise had almost disappeared.
The tech who'd done the cambelt and the service manager checked out the car and said the level of noise they were hearing was normal for a Citigo. To prove it they got the keys of two 18 plate Citigo's that were on the forecourt and truth be told the sound was identical to mine as it was when warmed up. Of course the only way for them to hear it when it's cold is to leave the car with them overnight.
Now it could be that the car has always made the noise when cold but I normally drive straight off somewhere and rarely idle the car straight after starting. Also, because you have to floor the clutch to start the car, you won't hear the noise unless you then release the clutch pedal. So the noise might have been there ever since I got the car but I've not ever let the clutch up before moving off.