A few months ago, my electric shower (Gainsborough EL900) stopped working (Seems to be no pressure). After that the pressure of the hot water in the bathroom has gradually become weaker. Now there is no hot water or central heating at all and the boiler (Vokera) keeps switching itself off afer about 10 minutes after reset. It will flash green for a bit then go back to red. I've tried to bleed the radiators, the ones downstairs have water coming out straight away but the ones upstairs will hiss a little bit, then nothing, no hissing or water coming out. Please can somebody help? What do I do?? Thanks M