Hi, I'm so pleased I came across this thread - I've been having the exact same problem for about two months. When I turned off the ignition the radio was staying on occasionally, and I had to restart the engine to turn it off. Interestingly, I've also been having a problem with the in-car Bluetooth - when I've been making calls the phone hasn't been disconnecting after the call has ended. Finally, when I've been locking the car, the display lights have been staying on and the time has been freezing until I unlock the car later/next day. I'd been worried because the illumination from the display and ambience lighting is really obvious and I was concerned people would think the car was unlocked.
Anyway, the battery drained so I called Green Flag who came out and jumped it. I mentioned the problem but they didn't seem too worried and said it might have been a one-off. Then the battery drained exactly a week later and they came out again.
As my car is still under warranty I booked it into Arnold Clark where I bought it last year (it's a 60 plate Fiesta). They were completely fine on the phone and said it sounded like an electrical fault and that they would sort it. However, two hours after I dropped it off I got a call from the garage saying that they would need to plug the car into a fault code reader which would be £60 for one hour, and if it showed nothing I would have to pay for at least another hour of this, and for the resulting work. They wouldn't even check the battery without payment - they said that the warranty doesn't cover any of that.
I couldn't really afford what sounded like it could be an endless pit of money, so I picked the car up and took it to Kwik Fit where they did a free battery check. They said the battery is completely fine and that it sounds like an electrical connection has gone wrong somewhere. They were surprised Arnold Clark wouldn't even look at it under the warranty.
Since I took it there, I haven't had any issues with the battery draining, but then yesterday the issue started happening again with the radio/lights staying on.
I've contacted Arnold Clark to see what they can do - I'm a complete novice with cars and a bit nervous about fiddling around with fuses! Should this work be covered under my warranty???