When you try using the oven, does the fan run?
Does the temperature light on the front come on?
Thanks for that.
It's not going to be the thermostat as the light comes on to indicate it's sending power to the element.
Isolate the power to the appliance. Disconnect it from the electrical supply
As the fan is running and the temperature light is coming on, then the most likely cause of the problem is a failure of the circular element in the oven.
There are other possible causes but not common, check the element first.
The method of changing will depend on the element fitted at the time of manufacture.
There are 2 types, one is held from the front by screws, the other is held from the rear by nuts.
Take the rear panel inside the oven out.
This will reveal the element and the fan.
Take the screws holding the element in place out.
Bring the element and the wiring into the oven cavity.
If the element is not obviously blown, you need to test it with a multimeter to see if it's open circuit.
Swap the wiring on to the new element. (Don't lose the wires into the back or you'll need to take the appliance out and remove the panels to retrieve them).
Fit the element in place and replace the cover.
Turn the power back on and set the clock.
Try the oven again.
If there are no screws holding the element in place, take the oven out and take the rear cover off.
You can now access the wiring and the nuts holding the element in place.
If the element tests ok, let me know.
Hope this helps
Let me know how it goes or if you need more help