Leave it to the British to hark back yet again to World War II and come up with 13 more hours of heroism on the home front. This time the chaps with the stiff upper lips are members of a London bomb disposal squad in a harrowing new "Masterpiece Theater" series called "Danger UXB."

UXB stands for UneXploded Bomb, and it's plain from the first episode, which airs tomorrow at 9 p.m. on area public TV stations, that we are in for an edge-of-the-seat three months of Sundays.

It seems that after the night bombardment of London began in the autumn of 1940, Londoners had to live not only with the whistle and crunch of German explosives, but also with an eerie aftermath: the presence in their midst of delayed-action bombs, many with booby-trapped fuses, buried deep in the earth and rubble.

At first, the police did what they could to defuse the UXBs, with little success, so the matter was turned over to the Royal Engineers. There were no textbooks, no instructions and no protection. A squad of engineers located the bomb and dug a pit around it. Then an officer went in and removed the fuse. If he was successful, the bomb was then hauled out and disposed of. If the officer was unsuccessful, the bomb disposed of him.

That sequence made it very difficult for bomb defusers to learn from their colleagues' mistakes. By the end of 1940 there were 4,000 UXBs, and the life expectancy of a bomb-squad officer was seven weeks.

Enter young lieutenant Brian Ash, played by Anthony Andrews, in his shiny MG sports car. He is a "direct commission" into the engineers, and rather expecting to go for training to Sandhurst. Instead, he finds himself in a ready room that resembles that of "Dawn Patrol," where fellow officers banter colorfully about the recent vacancies in their ranks and generally live as if there were no morrow.

"Don't people have to volunteer for bomb disposal duty?" Ash inquires.

"I don't think so," a fellow officer replies. "Nobody asked any of us."

Scarcely before he has learned the difference between a German 1,000-kg bomb, (nicknamed "Herman") and a 1.5-ton bomb known as "Satan," he is called upon for some on-the-job training in a deep pit.

Prodcer John Hawkesworth, who also brought us "Upstairs, downstairs," was correct in assuming that it is quite impossible to relax while watching an actor slowly turn the fuse of a bomb. Particularly when the first frames of this story show a similar young fellow meeting his maker in a spectacular fashion.

But Thames Television, which has already aired this series in England, is not above adding even more forthright human interest. Our hero Lt. Ash ("Ashes to ashes," a fellow officer greets him jovially at first meeting), spends his first night sitting out an air raid. Everybody else in his boarding house has taken shelter in a sewer -- except for a ravishing blonde with a sensitive nose and a pot of steamy tea.

"All the bombs going off makes me feel quite goosey," she confesses to him, as a blockbuster of two illumines the street outside the blackout curtains. Then she slips out of her nightgown. Lt. Ash, however, is a bit preoccupied -- and elects to head for the bomb shelter, leaving her to steam with her tea. Later in the series, we are informed, he is to fall in love with the less excitable but more plotworthy Susan, played by Judy Geeson as the daughter of a scientist who is trying to invent a safer method of bomb disposal than trial-and-error.

(Aside for Anglophiliac television watchers: Anthony Andrews married Georgina in "Upstairs, Downstairs"; Judy Geeson was Caroline in "Poldark.")

From the look of the first episode, "Danger UXB" is a cracking good television yarn with strong characterizations, an attractive hero, a nice authentic feel to its outdoors locations and a plot that ticks alarmingly at all times.