WHEN Margaret Thatcher addressed her Conservative Party's annual conference last week for the 10th time as Britain's prime minister, her supporters chanted, ``Ten more years!'' They may well get what they want. Already her country's longest-serving prime minister in this century, and unimpeded by constitutional limits, she is expecting to seek a fourth term in 1991.
And given an opposition in as much disarray as the Labour Party, despite the best efforts of leader Neil Kinnock to drag it out of the 1930s, she will likely win. Complacency is probably what the Tories most need to be alert to, but Mrs. Thatcher does have an agenda: reforms in education and the National Health Service, and a newfound interest in environmental issues and cities.
If she is judged on her ability to deliver peace and prosperity, her lease on 10 Downing Street should be renewable. As one of Mikhail Gorbachev's first big fans in the West, she has basked in at least reflected glory in US-Soviet d'etente.
She makes a strong claim for delivering prosperity to Britain, too - and rightly so, despite some clouds on the horizon. The economic scenario will sound familiar to Americans - strong growth and unemployment on the decline. But the recent consumer spending boom - or binge - resulting from tax cuts has led to serious trade deficits and inflation, which have forced increases in banks' base interest rates from 7.5 percent in early summer to 12 percent in late August.
Moreover, although a very broad range of Britons have seen their economic lot bettered under the Thatcher years - home ownership has risen markedly, for instance - a good many others have been left out of the boom, and Thatcherite Britain stands accused of greed and selfishness. There is a north-south split to this, too, with southern England prospering while areas of the north have high unemployment.
The split has been mitigated somewhat as soaring housing prices around London have forced many in the south to start thinking of cities as far away as Leeds, halfway to the Scottish border, as commuter suburbs of London. But a gap remains.
For last week's conference, in Brighton, England, Thatcher stayed at the same hotel where the illegal Irish Republican Army attempted to kill her (and did take the lives of five others) with a bomb in 1984. Since then, her signing of the Anglo-Irish accord has convinced a good chunk of the (largely Roman Catholic) constitutional nationalist community in Northern Ireland that Britain is there not as an occupying force but as an honest broker, to remain there as long as a majority of the people there so wish. This undercuts the IRA, and is an achievement.
Thatcher is resisting the ``United States of Europe'' idea being bandied about within the European Community as it moves to what it calls a ``single market'' by 1992. She favors the EC as a deregulated free-trade zone, rather than a cartel.
Economic integration of 12 sovereign states would have obvious difficulties even without Thatcher there to point them out. Even the proponents of a common central bank (which she opposes) can't agree whether it should be independent, like the German Bundesbank, or tied to an elected government like the Banque de France.
Still, the burden of proof is on the EC to show that the single market will not just be Fortress Europe. Mrs. Thatcher has taken heat for her outspokenness - the German weekly Die Zeit has called her ``Lady de Gaulle.'' But her contrarian position has given her clout with the Community.