Sampson brilliantly dissects Britain

It's hard on Britain's real-life upstairs/downstairs crowd. Now that young master India and the junior colonies have set up on their own, the big house is too stately. And without them to take care of, Lord and Lady Upstairs haven't settled on what to do next. They hope to find a role for themselves eventually.

They have proved to be excellent administrators but aren't attuned to producingm anything. Settling for a smaller house and a simpler way of living would be more efficient, but what will happen to Mr. and Mrs. Downstairs, their butler and cook, who have learned to expect the family to maintain them safely and securely all their lives? Besides, what about all those glorious memories built into the very fabric of the house?

That, if I read him aright, is the picture Anthony Sampson is showing us in his long (476 pages), highly informative book The Changing Anatomy of Britain (Random House, $17.95). The title is an apt one, with Mr. Sampson bringing his earlier ''Anatomy of Britain'' and ''Anatomy of Britain Today'' up to date. He lays bare the very bones of Britain, taking on its institutions one by one, and offering a bit of history, then taking an informed guess about their future. And doing it all with affection, sadness, and candor - not to mention considerable humor - but without many suggestions for arousing the old bulldog spirit, implying that only a change of attitude can do that.

He finds British enterprise held back by, among other factors, memories of the past (including a privileged upper class and a lower class protected by paternalism); red tape; and a new emphasis on bigness (big trade unions, big Big Business).

Splits between Southeast England (the wealthy stockbroker belt) and the rest of the country (especially the industrial North), between labor and management, civil servants (in protected, well-paid jobs) and the others (in uncertain, inflation-prone jobs) all hold back Britain's native vigor. Those of us who are British-born shrink from the notion that class and elitism still have a stranglehold on the country, but Mr. Sampson insists on showing us the facts and figures:

In 1977, 86 percent of the senior officials in the Foreign Office were from Oxford and Cambridge. And in 1982 ''the chairman of the BBC, the editor of The Times, the foreign secretary, the heads of both foreign and civil services and half the chairmen of the big four banks (were) Old Etonians . . . ,'' all linked in an ''Old-Boy network.'' Not, in his opinion, the best idea, since ''The old charge against Etonians was that they were confident, stupid and out of touch with the lives and needs of most of the country. The new charge is that they are confident, clever - but still out of touch.''

As for banks, the National Westminster, for instance, is ''a kind of monument to the past'' with its ''earl, two viscounts, three barons, a baronet and nine Etonians'' on its board. Even the newspapers, he claims, are divided by class.

On the other hand, engineers, so vital to the economy, are, according to Sir Monty Finniston, the former head of British Steel, ''rated below male models,'' and fall ''into a subordinate role like well-schooled butlers.''

''Perks'' (''about two-thirds of the cars on the road were owned by companies who also paid for the petrol'') put a brake on the economy. Secrecy (''one of the British obsessions'') hampers democracy, because, according to Lord Flowers, ''there's nothing like secrecy for stopping you thinking about things.''

Mr. Sampson's scrutiny of Britain's backbone - including the monarchy, Parliament, political parties, trade unions, schools, the law, banks, and industry - has obviously involved an enormous amount of research, but is well worth the effort it may demand of readers unfamiliar with the inner workings of Britain. ''The Changing Anatomy of Britain'' can be studied as a textbook. Or it can be dipped into for special information. (It is extremely well organized, with each page labeled to suggest its contents.) It's best to skip blithely over any obscure references - Sampson doesn't explain, for instance, who Alf Garnett (Britain's Archy Bunker) is - and go on to the next sentence.

Mr. Sampson's most endearing talent - to me, at any rate - is his gift for the telling phrase and apt quotation. And, since reviewing a book includes a license to steal, here are some gems I have picked up along the way:

* ''The modern monarchy is more realistic than most people who gaze at it: it is the emperor who realizes that he has no clothes.''

* '' 'I've always said about Tony (Benn) . . . that he immatures with age.' '' (Harold Wilson.)

* '' 'There are two kinds of people - those who want to be someone, and those who want to do somethingm.' '' (Dwight Morrow.)

* ''If America is a monarchy with an elected king, Britain has become a republic with a hereditary head of state.'' (Lord Hailsham.)

* ''For business purposes the boundaries that separate one nation from another are no more real than the equator.'' (Jacques Maisonrouge of IBM.)

And here is a quotation from Anthony Sampson himself that rings true to his American as well as his British readers:

''No one concerned by the inertia and irresponsibility of institutions could totally withhold admiration for Mrs. Thatcher, who insisted on the responsibility of the individual and who tried much harder than her predecessors to cut down the Whitehall bureaucracy and stimulate competition. . . . (But) she had virtually abdicated the responsibililty for mitigating unemployment. . . . The huge increase in British unemployed . . . could only be tolerated if it were accompanied by imaginative policies from the centre.''