A Cage of Ice, by Duncan Kyle
Solid little cold war thriller from around 1970. There's a bit of espionage and the second half becomes more of an adventure tale, which I find less interesting. But in the first half, when the protagonist doesn't know what the hell is happening to him, there are some lovely Raymond Chandleresque turns of phrase. "His nose looked educated."
There's a great scene where the hero, an English doctor, meets all the CIA guys and is startled to find that, unlike the spooks he's read about in English spy novels, they're all clean cut suburban dads. He refers to them as the PTA.
Overall a fun, quick, easy read.