British literary novel, probably published 1965–1980. Read in paperback around 1979–80.

A young man, probably middle-class, comes down to London from elsewhere in the country and lives with his sister possibly in Swiss Cottage. Over the course of the novel he gets drawn into heroin. The prose is literary in register, not pulp. One of the characters maybe called Turner — possibly a first name, possibly a surname. The phrase "man with the golden arm" appears somewhere in the text, almost certainly a conscious nod to the Algren novel.

Not Kops's The Dissent of Dominick Shapiro, not Trocchi's Cain's Book, not any of the obvious experimental 60s set (Quin, B.S. Johnson). Not the Performance novelisation.

Any ideas?