Worcester Bosch 25si not igniting?

Due to the recent very wet weather and strong winds, my boiler has gone into fault with flashing red light, I have dried the boiler out, but when running both with hot water and heating the gas burners ignite, the go out after 10 to 20 seconds, this pattern repeats a few times then goes into flashing light over central heating control, the burner light on the boiler does not come on.

Graham