Controller EP 2002 brand new. Boiler is an ideal classic FF260P?

The boiler is not responding to the controller instructions. When the hot water and central heating time periods are finished the boiler remanins on and keeps firing up thus the hot water and heating is on all the time. The only way to switch the boiler off is to turn off the electcity supply to the controller. We cannot find out what is wrong and we tried a new controller this has made no difference. Help.