ZANUSSI ZBB28651SA INTEGRATED FRIDGE FREEZER-FAULTS

I am not sure if anybody has had ‘issues’ with the Zanussi ZBB28651SA and can advise me on these issues but I am on my 2nd machine in short order and the second one has the same faults.
History-we had a Zanussi Integrated Fridge Freezer for 10 years and it was great but eventually failed; we [sadly] elected to replace it with the latest version from Zanussi and that was just shy of £700.00 to get it delivered and installed-big mistake.
New Machine[s]
The first unit was delivered and installed by the unit provider and the thermostat was set up by them to the correct setting with advice to ‘..leave it on that setting…’
We noted that the freezer fan was constantly running and only stopped when you opened the fridge section door. The freezer fan eventually started making horrendous noise and when the cover was removed, the fan was completely iced; the freezer draws [made clear for easy viewing of food] were all frosted over and the freezer section is not and never has been frost free as advertised- they are constantly frosted. After reporting the issue, the supplier sent an engineer and he ‘identified it’ as a control module fault and ordered a new one-that was on 7 weeks delivery. He then returned again, defrosted the blocked freezer again and replaced the thermostat control module in the fridge [this controls it all apparently] but this did not fix the issue and the freezing up/noise continued despite us turning it to it’s lowest setting; after a complete ‘fight’ with the supplier and Electrolux Zanussi, they sent the same Engineer and a ‘Manager’ from Eletrolux Zanussi, who autorised it’s replacement as it was deemed a fault with the temperature probe which is ‘inaccessible’ – 5 weeks later, they changed the machine.
The same thing started to happen fairly swiftly and we reported the issue. The engineer arrived this morning and he had a Control module with him! He changed that and then uncovered the freezer fan which was frozen solid. He borrowed a hair dryer from us to defrost it and told us to ‘give it a few weeks’
He left and within a short time we noted the fan running constantly again [stopping only when the fridge door is opened].Clearly there is an issue with this model of appliance-How on earth do I go about getting this changed for a different manufacturer? I cannot justify just forgetting about the £700.00 I spent on this- we only got the first one installed late in July last year.
Can anybody offer me some advice on this please?