How can I fix my Bosch KGN33V00GB Fridge Freezer?

The freezer compartment door was accidentally left ajar overnight, causing the freezer to slightly defrost. After it was closed the next morning, the unit made a lot of noise, dripping, tapping and noisy motor sounds. It was left, hoping it would recover on it's own.
After about a week, the freezer was working again, but the fridge wasn't cooling, and still hasn't been for weeks now.
Will defrosting the whole thing help, or is it more serious?
It is still under guarantee (it's 17 months old).