No problem! Yeah you're right about the security being at York House but they're kind of in their own little section, I could be wrong, but I don't think there are any rooms too close to them so corridor parties should be fine! York house also has a computer room which is really handy for last minute essay printing....
And no, unfortunately you can't pick which house but I don't know anyone who had a bad experience in any of them so you should be fine! Another plus is that many people don't put Park Houses down as their first accommodation choice so you'll almost definitely get in if it's your first choice. And even though most people didn't want to live there to begin with, everyone loves it once they're there!