I have a sabre 25he boiler just 14 months old , when it was 10 months boile?

Just looked at the technical manual for this boiler, if the green light is flashing on and off constantly, there is one of two things going on:
Either there is a HW demand (check for dripping hot taps rectify as necessary).
Or there is a back syphon occuring when any cold tap in the house is used/turned off, the resulting back pressure can make the HW flow switch briefly (firing the boiler), try fitting a non-return valve to the cold supply to the boiler.

Carefree
March 2011