How can I fix my zanussi model DF 56/45 ?

The freezer part of my fridge/freezer is slowly dying. The warning light has been on for the last two weeks and the temperature has been slowly increasing during this time. The temperature is now just below the fridges temperature. The thermostatat control and the fast freeze on the front have no effect. The cooling system at the rear is just warm but I haven't heard the compressor although it might be working.
Any help appreciated.