Meriva MPV engine just quits whilst running

Our 2012 Meriva with 101,000 miles will just quit whilst running. Usually this will be preceded by the engine stopping for a few seconds and then coming back on. This happened several times on a long road trip but we were able to drive home without stopping. The first time it failed completely, the AA engineer removed the coil pack and couldn't really see any problem but recommended replacing the coil pack because he had just that day had the exact same problem with another Meriva and had replaced the coil pack and apparently fixed the problem. The engineer didn't have a new coil pack to put on but once he had reinstalled the original, the car started up and drove to our local garage. They installed a new coil pack and the car ran fine for several weeks. Last week it happened again. This time, it stopped and the car coasted to a stop on the side of the road (this was on a busy motorway at 1 in the morning). It restarted and was driven for several miles before quitting again. It started again and ran for several miles before quitting again and then would not restart. An AA engineer then towed the car to our garage. He suggested checking for fuel and spark and thought maybe the issue was a crank sensor. Our garage technician checked for fuel and spark and both were present. Having a spark ruled out a faulty crank sensor. When he reinstalled the coil pack, the engine started and has been running normally for a few days. At this point we are wondering if there is a problem with the plug that connects to the coil pack. We now have no guarantee that the engine won't quit again and my wife is very concerned about driving the car. I also read somewhere that issues with the power steering pump might cause the engine to quit. Any suggestions?