Hi, I’m new to this.

i recently brought a Mk7.5 fiesta Zetec S (diesel) On cold starts (mostly mornings) it will run perfectly then 5 mins later (as I like to warm it up before making my journey) the lights will flicker and my radio will cut out. Then the car will stall/cut out. There’s no Bethune lights and I’ve a full tank of fuel. Is there any reasons to this??

Engine lights, sorry*

assuming you have all the lights on, heated seats, heated windows and the heater fan on max then I am purley guessing that the battery has not got enough volts in it to keep the ecu alive.

if you try another day to start the car and leave it running with nothing on for the time period and see if it happens, then the next day again but with 1 item switched on and so on each day turning more on until it repeats then I got it right! and you got your answer
Modern cars make everything as small as possible to save cost on manufacturing
back in the 70's the Japanese went to a 12mm bolt head instead of a 13mm apparently that save 1 million in 1 year
apply the same to your car nad the battery is as small as possible and so is the alternator

When you car is sat on tick over rpm the alternator is not charging the battery