Micra won't start - does not turn over

Hi Guys!

4 months ago i brought my first car.... a 1.0 Nissan Micra E, 04 plate.

After 2 months it developed a problem, when the car had been left out in the sun for a while, it wouldnt start, not even turn over. Then if you leave it a while (approx 30 mins) it will then start. All the lights showing on dashboard so all fine. It was a very rare problem until late - happening twice a week, in the most akward of circumstances!

I have had my alternator and battery tested - not those. I have had a new starter motor - not that. Now im being told it may be an ignition barrel or switch. Im being quoted 380 by nissan for a new barrel but aparently the switch is much cheaper. I want to know exactly which it is before i spend alot of money!!

Please, any help/advice would be grately appreciated.

got one like this the other day, different model car,, but just a corroded battery terminal. didnt look that bad either. owner said it even drove 100% better. pulled stronger ,