Hi David,
There's a load of info about this (it was quite recently discussed) on the NATS Interview thread, so you might want to ask there too.
I've just passed the final stage interview, and have been asked my *preference* for aerodrome/area but it seems to be decided based on everyone else's preferences and how many people they need for each at the time the college course starts.
As for final placement, they seem to ask you again what you'd prefer, but ultimately, business need comes first (you'll hear this a lot!)...
When is your Stage 3?