myson apollo boiler?

hi just replaced heating cotrols ie, programer,room stat,cylinderstat used a salus/glowworm controls and wiring centre . i have a cable spare / two wires red &black the black as ared tag on it when the controls ask for heat the pump kicks in and the fan. but the boiler wont fire up. checked at the boiler end and the connector block you have the mains feed going in and the other two wires going to the terminal block . the block is as follows L/N/E mains and the HW/CH/CHOFFand then ON and pump L/N/E the red wire goes to the terminal marked ON and the black/red tag goes to the terminal marked PUMP Live. when i disconnected it im almost sure the black/red tag linked with the frost/stat SL in the old junction box , not sure about were to put them in the wiring centre my boiler is a myson apollo 40s , the boiler worked fine until i changed the wiring box cheers dave.