If someone does happen to be blocking the escalator (say the 39 week pregnant woman pushing a big pram with a child holding on either side) wait patiently behind for the 60second it take to get to the top, rather then trying to squeeze past.

If you are cappable of taking the stairs, DO SO. Don't insist on using the tiny lift which sixteen different people with trolley's prams, wheelchairs, walking frames and small young children are waiting for.