Of course if light bulbs were heavily taxed, there would become
a black market in them......

Tax them at source. Then people can ship in loads from France, except, of
course, they are for 220V and will blow twice as often.

On the other hand, would people bother, particularly as the hassle of
importing them illegally just isn't worth it, as the alternative is cheaper
overall than what they're used to.

Perhaps the government would then introduce colour temperature
detector vans.

Another technological solution (easily bypassed, of course) to the silly
fittings rule in Part L1, is to introduce a pendent fitting that only allows
25W to be drawn. Any more and it should flash the light. i.e. stick a 100W
light bulb in and it has 1 second on and 3 seconds off. BTW, I'm not
actually serious here, except maybe if I renting out a house and wanted to
stop the tenant flogging the bulbs.

Christian.