Paco Underhill's "Why we buy" says that American shoppers tend to go right, but in the UK and Australia, they go left. He believes this is related to driving on the left, as the majority of people are right handed and are more likely to see and reach for an item slightly to their right.

If there are no references given in your document, I wonder if a study has actually been done of British primary school children to see if they really do turn left by default in libraries, or if someone is extrapolating from a study of adult shoppers? If it is related to driving, it seems odd that even primary children would have the same instinct.