IN FULL POSSESSION <i> By Helen Flint (St. Martin’s Press $14.95; 192 pp.)</i>

A despairing but wickedly funny novel about Thatcherite England, “In Full Possession” sets up shop in a run-down neighborhood in Sheffield. Television repairman Benedict Ashe is caring for his aged and infirm mother in their neglected Victorian house. The invalid’s chief comfort, besides the ministrations of her devoted son, is the memory of their recent visit to her daughter in Australia. The doctor advises Benedict that the only hope for his mother is take her back to the warmer climes of Down Under. Such an emigration could easily be accomplished--Benedict could raise the money by selling the house. (He already quit his job to nurse his mother, secure in the knowledge that at any moment he could have it back; the deeper the country sinks into unemployment, the more imperative it becomes that broken television sets be repaired within the hour.)

The single obstacle to the emigration is the sitting tenant in the Ashe house, Margueritte a schoolteacher who stands on her right to remain, rendering the house unsaleble. She has the law on her side in the form of an unctuous lawyer boyfriend; her refusal to see the human plight outrage Benedict’s sense of decency.

When Benedict’s mother dies, he blames Margueritte and vows revenge. Armed with the key to his tenant’s flat, Benedict undertakes to study Margueritte secretly. He reads her diary, examines her possessions, listens to her music and reads her books in an effort to find his enemy’s weaknesses. The more he learns about her, the more he plays on her innermost longings. Eventually he manages to seduce her. The game continues; he sabotages her friendships and makes her increasingly dependent on him. Margueritte is dimly aware of being undermined, but finds it difficult to distinguish the sense of insecurity from the abandonment of true love.

In this insidious struggle, Helen Flint ingeniously flips working-class/yuppie (yes, yuppiedom is international:, male-female stereotypes. As Benedict cuts Margueritte off from her level of society, he also learns to become the model boyfriend for Margueritte; after all, he has committed to memory the instructions in her women’s magazines. In a hilarious scene, Benedict “lets slip” his desire to have a baby in just the melodramatic manner a woman might: mooning, hurt that the feelings can’t be divined.

The trick of the novel is to keep the reader in the dark about how Benedict’s plot is progressing. With the brilliantly mischievous insertion of a parody on the omniscient narrator, Flint occasionally steps back to take a look at the larger picture. These ostensibly illuminating asides serve only to underline the mystery (“Not to worry: Ben is no psychopath”). The ultimate question is not resolved until the surprising climax: Has Benedict fallen in love with Margueritte? Has he forgiven her? Where is the line between love and obsession?

“In Full Possession” is Flint’s first novel published in America, and should gain her an appreciative audience.