thanks kevin sorry for just getting back! ...
Yes Just call biasi!
Rang them after having several quotes from different plumbers ranging from 150 -£300 and they said to try changing the thermistors first.
They also said the values of the thermistor were online (biasi website) so...
Hi I have the Biasi compact 28s when you switch CH on the boiler fires up for a few seconds then it pops off and displays a rapid flashing light. It does this some times for up to 12 hours repeating the problem every 5 minutes. Also when the CH is off via the timer the boiler just fires up...