2010 Citroen C4 car rolls forward and wont reverse

C4. Automatic. Car rolls forward when trying to reverse on an incline. So before the reverse gear has time to engage the car rolls forward about 2 feet then it bites in. I was about an inch away from the parked car in front. Scary situation as had no room to manoever forward as the continued roll had got me to the limit of space. Is this a problem with all the c4? Never known anything like it. Also having to keep handbrake on when stopping on a hill. Then pray it will go into drive before it rolls back!?? Just had its mot and the diagnostics didnt identify any problems. Wondering if this is the norm for this car or might it be a fault???