Try out your heating system now, don't leave it till it gets cold, then discover the pump or the diverter valve is jammed. Happens every year, about 10 all ring up the same day, to be told I can't come for a week. If the pump isn't sending water around the radiators, turn off the boiler immediately, if the impeller can be freed, it can carry on for longer, but if left powered up will burn out. If you can see a chrome disc with a slot in it, on the head of the pump, undo, a dribble of water will follow but no more. Then poke a slim bladed screwdriver into the hole, you should feel a slot on the impeller shaft, give it a twirl, then turn on the power, the pump should start to turn, then replace the disc.