When the Pevensies accidentally wandered back into England, they had been away for years (or perhaps even decades) and had only a vague recollection that they'd even seen the lamp-post before, which implied that they had forgotten. Why didn't they continue to express that kind of confusion when they got back? The book implies that they remember a good deal about what was going on when they left; for example, they remembered to apologize to the Professor for accidentally leaving the coats that they borrowed in Narnia.
The book also mentions that Mrs. Macready avoided the room. While I don't remember if it's explicitly stated in the text, I've always assumed that that implied that they remembered why they had entered the wardrobe in the first place (I could be wrong about that, though).
When they got back, did they remember "where they had left off" with their old life? Did they remember everything that they would have remembered when they left (e.g. what they had for lunch the day before they left, the fact that someone asked them to clean their room today, etc.)?
Similarly, after returning from Narnia in Prince Caspian, they apparently got on the train that they were planning on taking to begin with and carried on with their business. (Granted, their absence wasn't nearly as long that time).
While the texts admittedly don't talk a lot about their "ordinary" lives in England, there's no indication in the text as to their behavior being noticeably strange (with the exception of Lucy's return from the wardrobe). So, why did they remember as much as they did?