I was driving along and suddenly I had to do an emergency stop the car cut out and would not start again it turns over but will not start

A serious fault in the ABS hydraulic control unit or a possible wheel sensor problem. The dealer can run a test with an electronic analyzer (called a scan tool) to locate the fault..

possible causes are
crankshaft position sensor
cam shaft position sensor/s
ignition control module
broken timing belt/chain

I would look into your fuel relay. This is a symptom of it going out. If I am reading this right. As you are driving your vehicle all of the sudden stops and you have to coast to a stop. It then takes some time to get it to start again but turning over fine. If this is the case then what I said should be it.

Is the battery good in it?

I heave the same problem on my Corsa B 1.0 2000, engine cuts out, and whe it happens, I hear one of the relay under the right side of the dash buzzing. After a couple of minutes, starts like nothing happend.
So far I manage to find that the speed sensor is faulty, when I tap him the car stops. I order a brand new one, but I'm not sure that was the issue.
I order also a Opel Tech2 tester from ebay and it has to arrive next week, then I can see the error code.

o2 sensor

Not the alternator, but a fuel pump or fuel filter could be the problem. BUT it depends on the indications. A fuel starvation problem would act like it was lunging and then dieing out before it died. If it just dies out suddenly, then I would suspect an electrical problem like a coil pack or cap.

sounds like a faulty crank or cam angle sensor. When it isnt starting you should then check for spark to determine if its a fuel or spark problem.

loose or poor contact to battery terminal

the fuel pump may be getting hot and would explane it cuttung off a cheep fix may be chang fuel filter to make it easer for the pump to flow