There are so many issues at stake here that it's difficult to know where to begin. The people dreaming up these ideas are unelected civil servants, and the European Parliament has little power to block the Commission. Although a certain amount of lobbying can, and does, take place, EC rules and regulations seem to proliferate without rhyme or reason - and totally regardless of the consequences. Scientific opinion on the danger posed by leaded fuel is not clear-cut. Indeed, there's a strong belief in certain scientific quarters that unleaded is far more harmful.
Leaded fuel has been demonized because it destroys catalysts - it's as simple as that.
For reasons best known to themselves, the EC legislators decided that we would have catalysts, come what may. The fact that catalysts don't work properly in cold, northern European climates has been established beyond doubt. Margaret Thatcher, to give her her due, held out against catalysts for as long as possible on the basis of the best scientific advice. But, instead, catalytic converters were made mandatory. Such a fuel would protect soft valve seats in older engines, and would also give the required low emissions when used in lean-burn engines.