The British are so verbal. And so is their television. In theory, this shouldn't work. In practice, it very often and defiantly does: tonight, for instance, and on the two succeeding Wednesdays that the Public Broadcasting Service (PBS) offers a Thames Television production of Alan Ayckbourn's hilarious trilogy, "The Norman Conquests."

Ayckbourn wrote three basically independent plays - the first airs tonight at 9 on Channel 26 - about six characters in search of an argument during the same weekend. The first play, "Table Manners," is confined to the dining room of the country home at which they have convened. The second takes place during the same period of time in the living room and the third in the garden.

Thus in the second play, "Living Together," to be seen next week, we hear references to things we've already seen happen and things we are yet to see in the third part, "Round and Round the Garden."The atmosphere abounds with deceit, duplicity, accusation, recrimination and misunderstanding. Doors are forever opening and closing on embar-(See AIR, B3, Col. 1) (AIR, From B1)rassments, reprimands and holy acrimony, and through these portals pass poor rare fools. The only reason it gets dark at night is so they will have a chance to forgive one another and prepare for the next day's skirmishes.

In short, though "The Norman Conquests" is set in an English country home, it has frightening and very funny universal aspects. It is about life as it is lived everywhere and about the common bond that unites us all - the inability to comprehend much less understand one another.

Our hero, Norman, is an incorrigible puppy - a terminally rumpled Romeo who had planned a "nice dirty weekend" in East Grimstead with his wife's sister. These plans quickly go awry, in triplicate, and Norman, trying to make the best of things, succeeds splendidly in making the utter worst.

He is the kind of person to whom people deliver such endearments as "Norman, I'm warning you," "Oh Norman, how could you?" and, "Yes, I love you, too, Norman, but please leave me alone." Yet he's really the only man in the life of the three women, including his wife, he sloppily attempts to seduce.

As directed by Herbert Wise, who handled all 13 hours of "I, Claudius," Ayckbourn's plays translate surprisingly well to television, especially considering that they are extremely, compulsively talky and each confined to a single space.

Wise maintains an effortless visual flow and is especially adept at modulating the variety of shots without detracting from the spoken wit. Perhaps the elaborate structural gag and the large amount of time are excessive when one considers the essential frivolity of Ayckbourn's story, and yet he has a welcome talent for bringing affecting pathos to the surface of seeming farce. As characters, these absurd persons plural manage somehow to be both largely insufferable and entirely endearing.

They are all well played, but Tom Conti's portrait of Norman stands out even so. Conti has a charming shaggy-dog appearance that instantly brands him as unthreatening, even when wrestling Annie to the ground in the garden or licking the jam off Sarah's hand at the breakfast table. He isn't a bad boy grown up; he's a bad boy who will never grow up.

As Annie, who'd planned the weekend with Norman but then is forced by circumstances and relatives to cancel it, Penelope Wilton has an appealing Diane Keatonesque quality - adorably plain and unpretentious, slightly disheveled, patient and sweet. Oncoming tears are signaled by a trembling chin that is not nearly so coy as it may sound.

Penelope Keith repeats her stage role as the ever-suffering but unmistakably indomitable Sarah, who in another world would have been allowed to become the fascist dictator she aspires to be. Hers is a faultlessly orchestrated performance, but then so are those of Fiona Walker as Norman's self-sufficient wife Ruth - self- sufficient in every possible way except for requiring the sole disorder in her life that Norman provides - David Troughton as "dim, dismal and stupid" old Tom, and Richard Briers as Sarah's preoccupied husband Reg.

In London and on Broadway it was possible to see Ayckbourn's three interlocking plays on three consecutive nights. A week's lag between each may be too long for audiences to realize all the cross references and remember approximately what was happening in the dining room during a certain flare-up in the living room. Public television is such a willing slave to formats.

Still, there is a wealth of shrewd humor here and each play can be enjoyed on its own. The last, shot entirely outdoors on tape (the others were done in a studio) is probably the most frankly riotous. In the middle of the second, Reg complains, "The problem with this house is, there's no television," If there had been, of course, there would have been no plays at all, because the characters would have been suffering Dr. Solzhenitsyn's "television stupor" and been too busy to bicker. One wonders if television really killed conversation or just put new limits on domestic disputation