Betacom 30 heating fault?

18 month old Betacom 30, hot water function works just fine. call for heat and problems start. Pump & fan run ok, Ignition & burners ignite ok (flame led on), after circa 1 minute burners go out (fan & pump still running), boiler then goes into second attempt to fire up and burners light (flame led is not lit up!!) at the same time the ignighter is constantly sparking, after 30 seconds burner goes out and it goes through the same process before going into lockout (red led on).
My feeling is that the "flame sensing" is not recognised, does that make sense and if so, how can I check it out? Secondly the green wire from the flame sense electrode to the condensate trap, what does this do and is there a functionality check that I can do? OK genius's, over to you.
Cheers guys,
Alan