help me f10 fault?

the glowworm 30ci boiler is 3 years old and we have no heating and hot water and the boiler was flashing F5 we have replaced the the thermistor and power flushed the system and now it is flashing f10 and still it is not working. we have been told that the swicth board needs to be replaced i think they are trying to con me iam 81 years of age i have already spent 700 pounds and now want me to spend another 400 pounds on the board or bye a new boiler for 3,800 pounds, please please help me i cant keep spening this amount of money.