As a Londoner, I get frequently annoyed by tourists in London. It's a city where everyone is very busy, and for me, I may have a couple of minutes to spare between meetings on other sides of the city.
Tourists seem to forget that London is a city with regular people going about their business. Especially at some touristy stations (Tower hill, which also is a massive commuter change point), it gets really bad. People don't know which way they're going, so stop at the barrier, or even worse, the stairs, to look where to go. Or they go through the barrier and stop, causing me (behind them) to get caught in the barrier. Or they stand on the left of escalators. That's REALLY annoying. Some of us don't have the few minutes spare to wait while you stand two-by-two having a chat on the escalators!!!!
/rant