Hotpoint HS3022VL Intergrated Fridge Over Freezing?

Hi Can anyone help I bought a Hotpoint Fridge HS3022VL. It’s a tall integrated fridge with a cool air fan and an electronic temperature control on the right side. I have had the fridge for just under 24months.

Last week the fridge started freezing up at the back towards the top near the fan and I had to keep switching the fridge off overnight so it could defrost. I checked the fan and it appears to be working as when the fridge is on I can see the defrost areas just below where the cool wind blows down at the back is slightly thawed. The fridge has continued to freeze up at the back when it is on after a few hours, so and I have to keep switching it off during the day as even though I have it on a low cool setting it keeps freezing up and icing up all the perishables and I have to end up throwing my eggs and coldslaw away as they are rock hard.

Recently when I switched the fridge back off after letting it defrost overnight (sometimes with the door open) I will go and switched the fridge back on and a little later about 20-30 mins when I open the fridge again all the lights on the electronic temperature dial is flashing all together so I have to switch the fridge off, then back on to my preferred setting (8+), but again when I check later the temperature dial has moved to by itself to a colder setting (-4) or the lights against all the settings are flashing all together simultaneously.

Has my electronic dial failed and is this easy to replace myself? Or do I have to contact hotpoint for the rip-off £109 repair which I am loathed to pay on a product I feel should not be failing after 23 months especially as I paid £550 for it. Can anyone diagnose it for me please, I need some help here.