AEG Santo fridge freezer S 75408 KG8 fridge not cooling

:confused:AEG Santo fridge freezer S 75408 KG8

I noticed the fridge had gone from +5 to +12 - panic!

Checked the freezer was ok, switched to coolmatic function, no joy after 5 hours.
There is no ice formed in the freezer part and that is working perfectly.
I don't know it this means the appliance is 'dead', or if there is some kind of ice blockage in the evaporator unit (I think that's what it's called, but no idea where it is).
As this is frost free, does it for some reason need defrosting to give everything a 'kick start'?
Any help would be gratefully accepted please.