Frost Free Fridge Freezer Icing Up

If you find that your frost free freezer has an ice deposit like a glacier running down the back, it is normally due to the drain at the back being blocked, you will need to unload the freezer and pull it away from the wall, then there will be a drain pipe leading to a bowl on top of the compressor, the idea is that the water drains away to the bowl and the heat of the motor evaporates it away.
What happens is that the pipe becomes blocked and the water cannot drain away, all you need to do is remove the pipe and clean.