I heard today that a fellow working in the city of london got a written warning for using a 2 metre a ladder because it was tied or stabilised. He was informed that next time it would be a fine.
If this guy was employed by a window cleaning company, that is compliant with the regulations, then the written warning sounds likely (not the fine though).
Remember, the principle governing the WAHD is that if a task can be carried out from the ground, then it should be. Ladders should be a last resort.
If the guy in question used ladders (tied or not) as a first choice; then he's not complying with the WAHD.