Miele fridge not cooling

Hey,

Have a Miele fridge here that's stopped cooling stuff. It's about 10 years old now I'd say. Just a fridge, no ice box. It's been fine until recently. However, even with the temperature at 2C stuff doesn't feel chilled. A block of butter feels solid enough, but other items like a bottle of tonic water, cheese, etc, are not cool. It's a spare fridge out in the shed for extra stuff. I wonder if the warm weather might be affecting it, but it's been in the shed for years. There's very little in at the moment. At one point recently it was up at 9C, then down to 4C. 2C is now fairly standard.

Miele are quoting €130 to have someone come and look at it. I'm gonna look on Youtube for suggestions, but don't have taking it apart myself.