I think that one has to consider the two primary settings of both chapters. In the ending of chapter 2, the setting is the apartment that Julia and Winston share for their romantic escapades. This "love den" reflects a sense of tenderness as well as a daring foray into the world of emotional and sexual exploration. It is in this setting where Winston and Julia are both able to delve into themselves and the world around them. They engage in reflection about the thrush's song the first time they met, and think about the world around them in terms of beauty, song, and resistance. The setting is one in which there is warmth, primarily because the setting reflects the epitome of human emotion.
This is destroyed by the Thought Police when they apprehend both, beating them into submission. The setting of Chapter 1 in Part III is a holding cell. The presence of telescreens that shout instructions at Winston and instruct him on how to behave is a far cry from the reflective tenderness of the apartment both he and Julia shared. Winston is alone, isolated, and wondering what will happen to him. The setting reflects this in cold detachment. From the setting change, the emotional atmosphere in both chapters has changed, reflective of how the Party holds power over the citizens' lives. In this power is the denial of the personal, confirmed with the removal of the private exchanges between two lovers in the apartment and replaced with the institutional feel of a holding cell.