Its unlikely we can match up the model based on the picture, however if you look under the hob there will be a sticker with the model and serial number, in most cases its just a case of removing a couple of screws and pulling the over out to see the label.
However if this isnt possible, please send me the picture via just answer, or you can upload the image here, and post the link, and I will see if we can find a suitable knob which will fit on your appliance.
Apologies there appears to have been a breakdown in communication, if you can upload the image here, we can try and track down the unit, are you able to advise the rough date it was purchased to help narrow the down the model numbers.
This is still likely to be a challenge to find the exact model, however we should be able to recommend a suitable replacement knob, failing that if you provide your post code I can recommend a an engineer to come out and look up the model and serial number so you have it in future.
Hello Yvonne, my name is George,
Can you tell me if it is the knob, or the stalk that it fits onto that is broken?