I'm not sure why I'm not sleeping!!
I had this same problem happen to me several months ago. I booked it into the stealer and they told me the problem is that the engine runs at its least efficient at idle. So when the car is left to idle for a long period of time the engine management system is continually trying to optimise it and then this is when you get the EPC and rough running.
Since then I never leave the car idling for long periods of time and the problem has never reoccurred. Whether this is true or not I have no idea but it seems to have worked.
Unfortunately I now have a bigger issue around how the car is running.........

2 weeks ago the car went in for a service, 10k, and I told them that there was a slight smell of petrol especially when the heater fan was on. They checked it and said the high pressure fuel pump under the bonnet had a slight leak and needed changing. So it was booked in for the following week. They changed the pump and I collected the car and all seemed ok!
I did the school run, parked up and took my foot off the clutch and as it should the start/stop kicked in. As it was really hot that day I was running the AC so put my foot back on the clutch to start the car. The car then started to turn over but it was struggling to fire so I gave it a bit of gas and it started. Over the course of a couple of hours this happened 3 or 4 times. I spoke to the dealer who said that it might be a bit of air in the fuel line and it should clear itself if not bring it back in.
This was late Friday evening. So I'm in the car waiting at the station to pick up my daughter when I take my foot off the clutch (force of habit) then decide it's better to leave the car running. The car struggles again to start but it does. Then all of a sudden a warning message comes up, "error, auto handbrake not working" or words to that effect. Next thing I know the auto brake releases and the car starts rolling backwards. Thankfully nothing was behind me.
I call the dealer immediately but it's now nearing their closing time and there's no chance of me getting there in time for them to have a look at it. They suggest calling out VW Assist which I do Saturday morning. They turn up plug in the laptop and find that the car is misfiring on all cylinders but mainly cylinder 4. After about an hour he manages to clear the misfires but can't work out what the problem is. He tells me to book in with the dealer because it must be something to do with the work they have carried out.
Monday morning I take the car back to the dealer and it's now been there all week!! They have had a master technician working on it since Tuesday and he still can't work out what the problem is. The car is still misfiring and not running right and they have said that the fuel pressure seems to be too high. Thus far they have tried swapping out several items on the fuelling side of things and now they are looking at the air intake side.
I've got a courtesy car but it doesn't make up for not having my car for a week and the updates haven't exactly been free flowing. I intend to go down to the dealer on Monday and camp out until they can explain to me what is the next step.
I have had the car approaching 9 months and I'm really disappointed that this has happened. I've had countless fast Fords without a single issue so find this really frustrating.