A former English Language student (now a Doctor of Psycholinguistics--yippee!) and I were talking about doing a study of how people use and understand 'down' and 'up' in directions in British English. There are some issues with London, Oxford, and Cambridge having 'up' status for various people in various contexts, but there's also the question of whether 'down' is perceived as 'south' or if it's 'toward the coast' or if it shifts depending on whether you're on a hill or not.
There's been a lot interest in prepositions in Cognitive Linguistics, but I don't think this aspect of down/up has been examined. Part of the question is: do English speakers understand down/up to be 'cardinal directions' (i.e. like north/south). Something has been made of the fact that English speakers give directions with left/right, rather than north/south/east/west. Does use of down indicate that we are more aware of the cardinal directions than might be thought from the relative lack of cardinal direction terms in our language use?