Our heating and water is not working properly on our Myson Orion 60B boiler?

The heating and water was working fine until last night when we had the really cold weather. The boiler seems to be working ok but the water and radiators are not getting really hot, they are not freezing so some heat must be coming through. We are not able to have showers and the house is freezing, can anyone make any suggestions on what we can try to fix this. I'm assuming that the problem has been caused by the very cold weather.