Hello, just got my ford transit 2018 with radio entertainment en sync 3

But when I stop and turn the engine of, key out. All light radio en sync screen still works. 

Is this normal. Will it get off after a while

Thanks.

Does it then turn off when you open the door?

Not sure how things are in UK but in America, there's something called Engine Stop Start (ESS) and when your van or any vehicle comes to a complete stop the engine shuts off. dealership are NOT required to inform you of this in fear they will lose a sale. There's a few ways to correct this but it can not be shut off permanently as the Gov says this feature is suppose to help save fuel etc. But don't you believe it.  if you open the front hood, check for a plunger style device nearest to the front of the engine bay. if there is a plunger device, you can disconnect this and lay at the side of the engine bay or attach with a zip tie. The issue with doing this, you will have a warning light or message on the dash which says hood open tec. Then there's the button on the dash/center console which you'll have to press each time you start the vehicle. Pressing the button turns off the ESS system but only until the next time you have to restart the van.