How can I fix my Bauknecht freezer model GKMC 1347/2; AFB 712?

I have a Bauknecht freezer, model GKMC 1347/2; type AFB 712; which is continually in freeze mode. It does not cut out when set temperature is reached. I presume it is the thermostat but cannot find any information / instructions on how to replace or to find the correct spare part item number