Hi I have a 2014 ford focus 1.6 zetec diesel and have been having the same issue now for just under a year where I wake up in the morning and the battery is flat. I have changed the battery and the alternator and was still having the same issue. The last garage I took it to did a vault drop and said it was a drain caused by my stop start sensor so I have had that replaced and for the last 3 months the car has ran fine. But the past week the issues have come back to a point where I can pull up for work at 9 and by 12 the car wont turn over. Any help would be much appreciated please thanks.(also this morning when I went to take the key out of the ignition to stop the car the engine was still running and had to stall it to cut the car out)

Parasitic battery drain. Something is keeping the electrical system awake and drawing power.

I had the same problem a couple of years ago. There's a thread somewhere, but I basically pulled each and every fuse one by one while having terminals across the battery to measure the draw to find the culprit.

I seem to remember not finding an obvious reason but it sorted itself after that and I've not had a problem since.