If you have lived in London long enough, you really do get to appreciate how hard things get during the day to day hassle for tube and bus workers. When there is a tube strike, the buses get the full brunt of it. The amount of times I have seen business men and women, during rush hours in the morning, get angry at the drivers for being late, by 30 seconds or not letting them on because the bus IS ALREADY FULL AND THE DRIVER NEEDS TO SEE HIS LEFT MIRROR, is uncountable at this point. When a football match is on, they have to handle thousands of loud, and often out of control, fans and cause stadiums are getting bigger in London, they have to handle more and more fans each year. Just cause I pay the fare, doesn't mean a nice "thank you" wouldn't be needed. They aren't just responsible for you on the bus but many others on that same route.
Long story short, yeah I do say thank you. Especially to bus drivers who wait a bit cause they see me or anyone else running towards it. Yes, some aren't great but the rest are great at there jobs and do deserve appreciation.