I had to wait a few weeks for possible interview dates to come up on the website. They change occasionally too, i suspect when other people book or cancel.
I would suggest the best way to get to Swanwick (no guarantees) is to arrange visits elsewhere, and talk to plenty of people on the visits. You might eventually meet someone who knows someone at Swanwick. Maybe...
I have been told by three different people now that there is no point in trying because of security issues there, but it can't hurt, and what have you got to lose!
Good luck,
Andy