Sadly, the furthest I've been for work is central london. As I live and work in the suburbs, that's not really a massive change. That said, last time I went on a course, it was in the BT Tower, with a rather nice, if a little basic, buffet lunch in the revolving restaurant. Sadly, it wasn't revolving that day, but the views were amazing none the less.
A friend of mine though worked for a huge company in Canary Wharf. She was a tech support bod. One morning, she got a phone call. Something had failed in their regional office in Edinburgh. She was told to report to an airport, where there was a private plane waiting. I thought this sounded rather glamorous. She assured me it wasn't. They just wanted her to get to Edinburg, solve the problem and then back to London the same day.