Oven temperature. The oven doesn't heat up unless the temperature is set to maximum, I was

Question

The oven doesn't heat up unless the temperature is set to maximum, I was wondering if I need to replace the thermostat?I've found a part that matches my model at espares.co.uk, but I'm not entirely sure where to fit it...I've taken the oven apart a little to have a look - does it go in at the top behind the front panel which houses the dial k***s?Many thanks,Spencer