Belling Format 652 won't turn off?

Good Evening, I have a Belling Format 652 (Black). When the bottom fan oven is turned off the element at the back remains on and red hot. The only way to bypass this is by turning it off at the main switch. It seems that if the door is opened slightly this deactivates the problem also although still seems to be doing something? Belling have offered to repair the fault by registering us with a warranty for a year - £150 over 10 months. Is this something I can fix at little cost and if so how do I/part number etc?