If you're not sure if your oven is reaching the correct temperature, it's recommended to use an oven thermometer - as explained in this short eSpares video.
At eSpares we often get comments from customers who suspect their oven is not cooking at the temperature they've set it to. If you think the door seals in your oven are not sealing properly or you think there might be a fault in the element or in the thermostat a great way of testing is to use this thermometer
It's completely heat safe and can be placed inside your oven to give you a true reading of the temperature.
You can either hang it on the end of a shelf, like so, or it can be left to stand at the bottom of the oven.