Problems with car still under warrenty

Hi,

I bought a 03 Nissan Micra last May from a Nissan main dealer.

Since the day i got it , on particularuly cold mornings or on an odd occasion I have been unable to start it in the mornings. Basiaclly it turns over and shudders and dies.. I have to rev the car to start it then.

I have bought it back to the garage 4 times about this and they fix something each time but basically no difference. Currently it is in the garage now having another part fitted again.

So basically its not costing me anything now but it really irks me to ahve to organise to ge the car to the garage and sort out transport from the garage to work.And I almsot cry in the mornings with frustration over the thing when it doesnt start

So what is my position when the warrenty ends. I really dont want to have to deal with this problem forever with the car, even if they extend the warrenty for this problem seeing as it obviously was a pre existing condition. I would quite happily trade it in for a car of the same year with them in the mornign if they allowed it! Wht are my chances of that?