I think that there are several branches of this shop - on Saturday the one in Portobello Road was selling packs of ten 11W compact fluorescents for a pound, screw or bayonet fitting. Other things I noticed included a 9-LED torch (metal and quite nicely made) with three AAA batteries (zinc), mains timer adapter plugs, and fairly hefty bars of Toblerone, all at a pound each.
I think someone told me that (ignoring travel times) it actually takes less energy to travel from Earth to Mars than between Jupiter's moons. Can anyone point me at a source for this? And for energy requirements for other interplanetary journeys? Preferably something that I can use without breaking copyright?