If you look at the vent inside the freezer were the door switch is do you see a build up of ice in there?
Ok if the fan is working ok then its proberly a blocked evaporator inside the freezer.
As how the fridge works is it gets its cooling from the freezer section. The fan blows the cold air up into the fridge section. So if the freezer is working and the fan is its going to be a blocked evaporator stopping the airflow into the fridge section.
What you need to do on this is a full defrost. Turn the appliance off for 24 hours and keep the freezer door open.
This will allow the ice it melt in there.
Then 24 hours later turn it back on and hopefully this will get it going.
But if it does it again say in 3 weeks time then its a defrost problem. More then likely a defrost heater. This will need to be replaced to cure the fault here.
So try a defrost and see how it goes..
But even if the heater is faulty this can still be repaired so theres no need to replace it.
If you need anymore info just get back to me.
No worries try the defrost and let me know how it goes.
Nice one glad to hear you got it sorted and thanks for letting me know.