"One day I noticed that the washing maschine was using warm water (it's
OK to do
that). I changed it to use cold water. From that day water has come
warmer much
sooner and stays warm longer. I haven't changed anything in the boiler.
I even
changed the washing maschine to use warm water again and sure enough
taps turned
cold as before. "

Are you saying that this is was the cause and fix for taking a long
time for hot water whether or not the washing machine was actually
running? If so, that makes no sense.