THE British Airports Authority, or BAA as it SHEEPishly now calls itself, comes to support Cecil Parkinson's case for new kinds of privatisation. County Bank's idea of making the institutions tender for their shares looks an idea which has come to stay. That apart, here was the privatisation to please nobody. It does nothing for competition, by putting the three main southeastern airports together, leaving them free to cross-subsidise each other, leaving their airlines to be allocated by official patronage, leaving their income dependent on the tax concession for duty- free sales. It does nothing for the State as — apparently cheap — seller. It does nothing for the small investor, who gets an uneconomically tiny parcel of shares which, if he tries to sell them, will see all his profit disappear in dealing costs. It does nothing for the stock market, which must now try to handle another two million pieces of paper, the BAA allotment let- ters, just when the paper mountain in brokers' offices threatens to become an avalanche. It does its bit for what the Treasury likes to call 'negative public expenditure', but its chief use must be as a compendious example of how not to priva- tise.