No, cyclists are not legally bound to use them. I sometimes don't use them, because a significant proportion are clearly designed by people that don't ride bikes and are not fit for purposes. Many of them aren't wide enough for two bikes side by side, meaning no overtaking and being stuck behind...
Does this actually get enforced though? I think we have something similar here but I've only ever seen one copper stopping cyclists, and then it was for cycling the wrong way down a one-way street.
I would love to see much more enforcement of the rules around cycling - the idiotic minority give...