I have the twin oven model and when I try to use it cuts out after about 15 mins, being a bit dim I have replace the main oven thermostat, but realise I should have ordered 2, one for the top oven as well. Have replaced one and sent for the other, but jus wondered if anyone else had had this problem and am I correct in thinking it is the thermostats at fault....please help as my kids are getting fed up of beans on toast!