Hi, I have just moved into a new flat and have been left an Ariston microgenus 23 MFFI combi. The hot water is perfectly fine but the central heating cycles on and off constantly then goes into lock-out every so often. There are a row of LEDs indicating temperature, on the front. It generally starts cycling around 80c, which I would suppose to be normal. However, the boiler locks out after a few minutes. Any help would be very much appreciated