The most likely cause is the thermostat has failed, and not regulating the temp in the fridge correctly.
A replacement thermostat can be purchased for £35 here.
If you would like me to recommend a engineer in your area to fit it for you, please provide your postcode.
Good evening, I havent heard from you in a while, do you still require assistance?
I would recommend first call on 01233 640062, we have referred customrs to them in the past are very reliable.