Ah, you tried to eat all the bread while avoiding the peanut butter!
Smiley's People is, chronologically, the one in the middle. Though they can be read out of order, they make the most sense sequentially. That makes The Honourable Schoolboy a weaker novel, because it relies on the set-up from the first two to build plot structure as well as sympathy for and knowledge of the main character, but I found it to be a fine way to pass an afternoon even so.