Your Boiler has reached the end of its life i'm afraid, so will need repalcing ASAP, Please be aware that if water is dripping on to the burner, cooling the flame this COULD be creating a dangerous level of Carbon Monoxide!
Please get this boiler looked at by a RGI urgently
www.gassaferegister.co.uk
will assist you to find a local engineer
www.elanar.co.uk, August 2009