Hotpoint HM315FF BUILT-IN FRIDGE FREEZER

Our Built-In Frost Free Fridge/Freezer model Hotpoint HM315FF Ser No. 009180081 – 81537410000 has recently been making a “clicking” noise from the internal light, and at the same time the light would switch off and on, finally the light would go out completely and the fan would stop working. Eventually, after about half an hour we could hear the fan and compressor start up.
However, several days ago we noticed that the light failed to work, and there was no sound from the compressor. Ultimately, we could see both the fridge and freezer were de-frosting, and we had to empty the appliance and pester neighbours to store our food.
I checked the power supply from the socket and the plug fuse both of which were working. Having left the appliance overnight (still switched on) and with it being out of service for approx. 20 hours, I opened the door the following day to check for telephone numbers and immediately the internal light operated as it should, and the compressor could be heard to start up. Eventually both the fridge and the freezer reached its operating temperature sufficient to allow us to re-fill the appliance with food.
The appliance is still behaving in this chaotic manner with the clicking and light flashing when opening the door, the fan and compressor will cut-out. The appliance has "de-frosted" i.e. necessitated removal of food twice, and is therefore completely unreliable.
We have referred the problem to the Hotpoint "Technical Services". Their technical engineers? have suggested we remove the décor door because they think the door switch is not being activated properly. Even though I know that to be hogwash, I have disconnected the décor door but as expected the appliance still behaves the same.
I have read of a similar problem online with this appliance, where the call-out engineer has replaced the pcb without any success.