2008 Vauxhall corsa cdti struggles to start and goes into limp mode but once running it drives great until you switch it off it may start first turn of the key or it will play up got told it was water damaged ECU so sent it away to be repaired but the fault is still there and the car is not showing any fault codes anyone ever had this problem 

I would be checking the Crankshaft and Camshaft Sensor(s) also the MAF Sensor as these could be starting to go faulty

More than likely to be a sensor fault more than anything