In case anyone finds this looking for an answer. Having changed the IAT sensor and other things the P0111 fault returned along with start-stop error. I thought the next thing to try was the battery, as I read somewhere that low voltage could cause P0111.. So, I replaced the battery with a new one and unfortunately the EPC fault returned. I was about to give up and take the car to a garage when I found a Polish YouTube video that showed that on the 1.0 TSI there are actually two air temp sensors; one on top of the engine and one on the side towards the battery. I had changed the one on the top and it had made no difference. Hence, I refitted the old sensor there and fitted the new sensor (same part number) to the side of the engine. Since then, the EPC P0111 fault and stop start error have not returned (2 weeks). I hope this helps someone.