Leaky wc cystern,So I turned water off on water meter, and on valve at bottom of large storage tank in loft. Did repair. Turned the two valves back on and open. Now I have all cold taps flowing, but have no flow on any hot taps. It seems an air blockage problem. On the top floor I tried blowing up hot tap, and introding water from the cold tap to the hot tap with a hose and that can work. I got a bubbly air water sound but still no water. Where else should I look. I don't recall turning any other valves off.