I have a Mira electrical shower which we inherited with the house 5 years ago. It worked fine until a year ago then the low water pressure light would randomly come on and no water come out. It resolved itself bizarrely but a few weeks ago it started doing it again. Sometimes it will work for a minute or two, then stop working. Other times the low pressure light comes on immediately and it dribbles a few drops of water and nothing else. Please can anyone suggest what might be wrong with it please?