Turn off and let warm up. Then restarted fine. After 12 hours warmed up again.
Kit Erlebach
I will try and help with this problem John Lewis JLFFW2013 fridge freezer
This sounds like it may have a problem with the defrost system and ice is building up and obstructing the airflow to the fridge compartment. I have included the video for you to watch below.
John Lewis JLFFW2013 fridge freezer

