Following on from other thread had the boiler (Thorn Apollo 15/30) serviced and the TC changed and the Oheat stat replaced, the guy changed some 'A' clips so that the cowl pulled tight against the back as the old clips were threaded and all seemed well the boiler fired up and we have had heat and HW for 2 days now. BUT Now the boiler won't light AGAIN it's gone out and won't relight, now it seems the Oheat stat is gone again but I don't want to keep calling someone back to just change it so it works for a day and pops again. Why would the Oheat stat keep going? is it meant to fail safe or is it meant to cool down and reset? or is there something else? The Stat he replaced was on the left hand side above the TC and buts up against the heat exchanger, he didn't change the Low stat where is this? should it need changing?