shiner i know exactly what you are saying but you cannot have one law for one trade and another law for another, if a painter was to do that job he would use a ladder true it would have a anti slip device fitted so if a window cleaner decided to use same method who could complain these are only my thoughts and may be i will be proved wrong but how can H & S police these rules on domestic properties.
The laws aren't trade specific of course. I suppose that a scaffold tower might be the way most cost effective way for a painter to avoid ladder use. For what it's worth, I don't actually agree with the new working at height rules either. They seem too inflexible to me. I feel that maybe compulsory, certified ladder training would have been a better way. Although I have plenty of ladder experience, I'm sure I would have learnt something from it.
As for policing the new(ish) rules, don't be so sure. I know for a fact that social security investigators travel around randomly and view people working. They then see what vehicle they are using and identify them that way. Of course, you and I never hear about that because once they check our IDs, check that we're not claiming and cross reference that we are registered with the IR, they don't pursue it. Also, if they do catch someone, the assumption is always that it is from an anonymous tip-off. If the powers that be can do that, it wouldn't take much imagination to do the same with anonymous H & S inspectors.
In truth, I do sometimes resent the fact that it was made so difficult for me to use my preferred work method (ladder) but having said that, I feel that I have made good use of the remaining choices. Having taken that plunge, I would feel quite aggrieved that a customer was trying to force me back to a method that I have now grown unused to.