Samsung fride-freezer problem?

My 3 year old Samsung fridge-freezer (model RL33SBN) seems to run ok for anything between 12 - 24 hours but then cuts out and stops running. The power is ok, all lights internal + external are fine and the motor seems to run ok. It may just be coincidence but the fault has started just after the mains power in the house was switched off due to renovation work. My hunch is that the thermostat may be faulty but any advice would be appreciated before going ahead and buying a new part. Thank you