I was booked for ceasarian a week before my due date and went into labour the day before caesarian was booked.
My midwife had told me beforehand that if this happened I would have C section anyway.
HOWEVER in between contractions when I was on operating table in hospital, getting ready for epidural or ceasarian I cant remember which, the doctor asked if I would prefer to give birth naturally as baby was doing well etc.etc.!!!!!!
NOW - I had spent the whole pregnancy not expecting to have to go through labour and no preparation for labour, not good with pain, so this was NOT a good time to try to make this decision.
In my previous labour I had ended up with emergency caesarian and baby in special care so this time I went for caesarian.
Baby arrived and had much smaller head than the first so its possible that would have been OK for normal labour. But I will never know and am happy that I went with caesarian.
So in answer to your question, what happens - probably is a local decision based on your reasons for C section and the local policy, but be prepared for anything!