Indeed. A 230V bulb would be useless everywhere, as Europe still has 220V or
240V, depending on where you live. The purpose of the legislation is not to actually harmonise supply voltages, but to ensure that every electrical device bought in Europe can be used in any other European country. As incandescent lightbulbs are so voltage sensitive, extremely cheap to replace and would be horrendously expensive if made to cover such a wide voltage range, they are exempt.In any case, GLS bulbs should be taxed at 5-10 pounds per bulb, IMO. You'll only get short sighted mathematically challenged cretins to buy proper bulbs if they see the cost in the purchase price.
Christian.