I have a Hotpoint Mistral Model FF72S which is about 9 years old. The freezer temperature readout has recently gone berserk! It will read up to +44C but reverts to -22C when the fridge door is opened. It seems to me that the fridge is running most if the time. There is an ice build up on the floor of the freezer which I have cleared out but this returns after a few days. Also I notice puddles of water on the floor in front of the fridge/freezer from time to time. Although I am not a qualified repair engineer I am very practical and could I’m sure repair this with a little help i.e. what is the probable fault, what do I need to repair it and any hints on how to repair it.