Anyone travelled out of the US before?

I will be going to England for Spring Break, as most of you probably already know.

Well, I have my passport but now I'm trying to get a straight answer on if I need anything else when I get to Heathrow but so far, I haven't gotten a concrete answer from anyone. I will be a tourist, on vacation, nothing more, nothing less. At the rate I'm going, in addition to my passport, I will be taking with me:

- Bank records
- letters from my boss and the Dean of Student Affairs saying I'm a student who is doing the tourist thing and have been given time off to travel.
- My shot records
- A full on Itinerary of my trip (was making that anyway, so, you know, not too hard there)
- My trip itinerary from my airline.

If Anyone knows a concrete list of things they ask for, I'd really appreciate it. Thanks.