Worcester Bosch boiler - flashing blue light?

I have a WB 15Ri RSF Greenstar condensing boiler (3 years old next week) and have had a couple of problems. The first being the condensing pipe freezing when we had the bad weather and now it has stopped working again.
The control panel says the heating is on but the radiators are cold and I have no hot water. The boiler light is flashing blue. I turned to reset and also turned it off but when I restart it the blue light stays on but only for a short while. The boiler makes a clicking noise (as if trying to light) and the on/off button flame indicator light flickers to green but then fades away.
Does anyone have any ideas on what may be wrong?