Today afternoon I heard some loud banging noises from the pipes/boiler. Ever since I have no central heating. I have a 8 yr old Potterton Suprima 50 boiler which now has its green light flashing. I turned off the boiler and switched it on after about an hour. Again I heard these loud bangs. I even saw the pipes near the cylinder vibrate. The noise was so loud I decided to switch of the boiler again. What's happening? Help pls.