A £100 penalty would discourage people from ringing in genuine emergencies until they are sure, costing lives in the process. ie is the house on fire or is it a bonfire in the garden or chimney, or is has that car run off the road or just been parked in a bad position. If people had to wait for doubt to evaporate, they would likely carry on with their business and ignore it. Look what happened in china when a judge ruled that if you take an injured person to hospital you must feel guilty (and therefore have caused the accident) - it resulted in people ignoring a child who had been run over by a van (who died btw).
Best course of action is what they do, from time to time publish the silliest ones to remind people. The control room can cope with turning them away, its not like 3 appliances turned up to get that womans teeth out the road is it?