Ive noticed that my R56 Cooper has really bad idle when the weather is colder on cold start ups - like its not staying at a certain level its all up and down sounds like it will cut out

its a bit embarrassing really! Sounds like a really old car

what could this be?

Its going in for a service on Wednesday...

Perhaps the fuel pump. Mine acted up on cold starts but ran fine any other time.

Dealer said its possibly the vanos adjustment? dirty vanos solenoids that need cleaning - is this a hard job? does anyone know?