From my own experience i have found that those of us at the Airports tend to wear slightly smarter clothes than our colleagues at the centres, shirt and Tie is commonplace all be it hardly formal.
I really don't think clothes should be an issue, we do not have a public persona so I think we should be comfortable rather than formal.
My personal dress wear tends to be smart casual as that is what I feel is appropriate but I do believe in each to their own.