i wouldn't put all your hopes on swapping, when i was in lancaster house most of my floor had put it really low down in their choices and wanted to change, and a couple of people rang up/tried to swap and naturally there were SO many more people wanting to swap from park houses/village to posher ones than the other way round, so it just doesnt work! park village is fine, if the ensuite is what you're worried about dont be, its really really fine sharing a bathroom (unless your home is swanky, you've been sharing all your life anyway!), and out of the two i'd much prefer to live in park village, simply for the campus location- stanmer is a bit of a pain i think, and seems quite out the way, being separated from campus by an underpass.
by all means try swapping, but i wouldn't assume anything will come out of it!