Well Lucy, the white marks are usually mineral deposits, these are usually caused by overhead overflow pipes or lawn sprinklers. Tap water that is constantly pouring on the glass and left to dry will leave a limescale build up.
If you can't reach the windows with a ladder, they really have no option but to let you inside if they want them doing.
The white stuff on the rubber is only french chalk and will wash off in use.
Hope this helps. Dai