Help re Freezing Belling BIFF7030E

Hi Folks. Wondering if someone out there could provide some guidance reference a Belling BIFF7030E integrated frost free fridge freezer. Problems with this unit started when we noticed clear ice forming to right hand side of rear fridge panel. Items placed to rear of fridge also started to freeze up – adjusting electronic temperature settings made no difference. The red warning led was also continually flashing. After checking that drain channel was clean and clear we cleared the fridge freezer and switched it off for 48hrs in the hope that that may reset it. On restarting the unit it was left empty for 24hrs. After this period, whilst nothing was placed in the freezer unit, some items were placed in the fridge. Within 12hrs there was a covering of ‘snow’ on back wall of fridge and a 2 litre container of milk had frozen solid. The display showed that unit was at mid temperature settings. The alarm led continued to flash. Door seals have been checked using pencil dust and appear to be sealing completely around door opening. Would it be worth trying a replacement PCB – if I can get one – of should I just replace the complete fridge freezer. Thanks in advance.