Hi again, I have read more about this problem on this Forum and others. Unfortunately it is a lesson learned regarding Fridge Freezer single thermostats and the way they react when the ambient temperatures falls below the the Fridge temperature - they stop freezing the Freezer! So we moved it inside the house and put a temperature gauge in both the Fridge and the Freezer and the temperture in both are correct. We have decided to sell the Fridge Freezer and buy a decent Fridge for the garage - without a Freezer box.
Thanks to this Forum for providing the info' I just had to convince myself not to buy a new thermostat costing more than what I paid for the Fridge Freezer. Cheers.