I have a Mira Advance ATL thermostatic electric shower. The shower has worked well until a few days ago. The shower now gives a high flow blast of water for around 5 seconds, the low pressure light then comes on and soon after that the flow ceases and the stop light comes on. I've turned up my mains stopcock to see if that was the cause, I've cleaned out the shower head thoroughly and tried without the shower head on and tried high, medium and low flow settings but still no joy. The service light does not come on during these episodes.theres no blockages no limescale all stop valves are clean is it time for a new one as its over 12 years old, can anyone please help